This is way more fun than icing a cake! I do thin the paste just a little with about a teaspoonful of water to 1/4 cup of paste. You want it to flow nicely but not to flow out too much – it should hold a nice peak. I like to use a #2 tip that you can buy at a kitchen or hobby shop. When piping, hold the tool at a slight angle with the tip gently resting on the surface. Squeeze and pull at the same time for a nice even line. The quicker you pull, the thinner the line. A thick dot of paste will take a good 24 hours to dry. Don’t be tempted to use a blow dryer unless you want the paste to do a lot of cracking. Finish your piece with clear wax or varnish as usual when it’s totally dry.
Transfer a line drawing to your painted, but unwaxed surface and then go for it! Here are some examples- the first one is a line drawing that you can download and use as a test piece: