Glowing glass baubles, a rainbow of colour and a sprinkle of galaxy sparkle: this watercolour ornament card is the kind of holiday mail people keep on the fridge long after the season is over. It's a joyful, low-pressure project that teaches you wet-in-wet blending, glazing, brush lettering and crisp white highlights, all on one little card.

In this tutorial from Strathmore Artist Papers, artist Leslie Tieu (Leslie Writes It All) paints a string of rainbow watercolour ornaments, letters "Spread Joy" in colour, then finishes with glazed patterns, sparkling stars and pen details. Watch the video, then follow our step-by-step notes and supply list to paint your own.

We've matched Leslie's supplies with what's on our shelves. Where we don't carry the exact product, or the video doesn't name a brand, we've picked an Opus favourite that does the same job.

• Cards: Strathmore Watercolour Cards, 5" x 6 7/8": pre-cut, pre-scored 140 lb cold press watercolour cards with matching deckle-edge envelopes, so you can paint, fold and mail. Making a big batch? Grab the 50- or 100-pack.
• Paint: Opus Essential Watercolours Compact Tin Set of 12 (in place of the Daler-Rowney Aquafine 24 set from the video): vibrant, vegan-friendly colours that re-wet beautifully. Opera Rose, Hansa Yellow Medium, Phthalo Green, Cobalt Turquoise and Ultramarine Blue cover your rainbow. Titanium White is there for the galaxy dots and sparkles, and Mixing Gold is perfect for the ornament caps.
• Brushes: Princeton Velvetouch Series 3950 Round, size 3 for painting and lettering. Add a size 1 if you want an extra-fine tip for the sparkles.
• Black pen: Sakura Pigma Micron Pens: archival pigment ink that's waterproof and fade-resistant once dry. A fine nib like 01 or 03 is perfect for strings and outlines, and a 05 works well for drop shadows.
• Sketching: Opus Essential Graphite Pencil Set of 6 and a General's Kneaded Eraser.
• Practice paper: an Opus Essential Hardbound Sketchbook or scrap paper to test your lettering and colours first.
• Optional: a ruler for the strings, a roll of washi tape to trace circles, and Finetec Gold Metallics if you'd like shimmering caps.

Pencil in your message first. Leslie wrote "Spread Joy" along the bottom, but a family name makes a lovely personal gift. Then sketch a row of hanging ornaments above it. Mix large and small circles, stagger them at different heights, and tuck a few behind others for depth. Freehand circles add charm, but if you'd like them rounder, trace the inside and outside of a washi tape roll for two different sizes. Add a small cap to the top centre of each ornament, then step back and check your spacing.

Use a ruler to draw a straight line up from the centre of each cap, keeping the strings parallel so nothing looks wonky. When you're happy with the sketch, roll a kneaded eraser over everything. It lifts most of the graphite, so the lines guide you while you paint but won't show in the finished card.

Work left to right in ROYGBIV order: reds and pinks, oranges, yellows, greens, blues, then purples and pinks to finish. Paint each ornament with two neighbouring colours, such as orange on one side and yellow on the other, and let them blend wet-in-wet. While the paint is still damp, dot in a little white for a soft galaxy effect.

• Keep ornaments distinct: let one ornament dry slightly before painting the one next to it, or the two will bleed together.
• Use plenty of water: it lets the colours mingle and create unexpected blends.
• Make it yours: swap the rainbow for the colours of the ornaments on your own tree.

Follow the same rainbow order for your lettering. Leslie paints "Spread" in monoline block letters, with an even thickness throughout and each letter in a different colour. "Joy" is brush lettered: press down for thick downstrokes and lighten up for thin upstrokes.

Paint the ornament caps in a warm, golden tone. Leslie uses yellow ochre, which hints at gold without being metallic. Mixing Gold works beautifully here, or reach for a metallic watercolour for real shimmer.

Once the ornaments are completely dry, paint stripes, zigzags, scallops or dots on top. Layering paint over dry paint is called glazing, and it adds depth and colour. Stick to the same colour family as the ornament underneath, like blue over blue. A different colour underneath can shift the colour on top. Look at the ornaments on your tree for pattern ideas, and don't feel every ornament needs one.

Pick up white paint straight from the pan with very little water so it stays bright and opaque. Paint a curved highlight where light would hit the glass, then add tiny stars: one long stroke down and two short ticks across. A few scattered dots complete the galaxy look. Use a very light touch, and switch to a size 1 brush if you want the finest tip. Watercolour dries lighter than it looks wet, so go back and brighten your highlights once everything is dry.

With a black pigment pen, draw in the ornament strings. Then loosely outline the block letters, slightly off-centre so a little white peeks through. This gives pale colours like yellow more definition. For a final touch, add a drop shadow to "Joy." Imagine a light source in the upper left, then draw a thin shadow line on the lower right edge of each stroke.

• Want more sparkle? Paint your ornaments with richer, more saturated colour. Bright white stars pop much more against deep colour than pastel washes.
• Let it dry before you ink: pen lines on damp paper can feather. Pigment ink won't smear once it's dry, even if you add more paint later.
• Know when to stop: as Leslie says, at some point you step back and decide you've added enough. Simple galaxy ornaments with white highlights look just as lovely without patterns.
• Practise first: try your lettering and a test ornament in a sketchbook before you start on the card.

Painted your own watercolour ornament card? Tag us on Instagram. We'd love to see it.