To paint the lines I used black gel colour dissolved in a tiny amount of water.
If the paint is very thick you will get broken lines.
Don’t add too much water, otherwise the paint will be runny and it will be difficult to make precise lines.
Test the thickness of the paste on a spare piece of paste.
Don’t apply too much paint on the brush. If there’s a blob of paint sitting on the end of the paintbrush, touch it to your palette, roll and drag it until no drip remains.
To steady your hand, rest the palm of your hand f.ex. on the table or board. Don’t hold the hand high in the air without any support, otherwise it will be very hard to paint straight lines.
Use a very fine paintbrush (f.ex. rigger). If the paintbrush is thick, you will get thick lines.
You can use an edible marker to draw the lines but:
It’s easier to make straight lines with a paintbrush than with a marker.
It will be harder to draw the lines in less accessible areas, than if you were using a paintbrush.
The paste needs to be very firm or completely dry, otherwise you would make indentations with the hard tip of the marker.
Paint the lines on the body and the head, before you attach the head.
First make the lines on the back of the head. Let them dry. Once they are completely dry, flip the head to the other side and make the lines on the front (face).
Stick the eyes (white cut-outs) before making the lines on the face. That way it will be easier to space out the lines properly.
Stick the thin, black sausages around the eyes after painting the lines and letting them dry.
Since the design of the cake topper is simple, try to keep the webbing quite simple too (not too many lines, not very close to each other).
You can use a printed image as a guide. Print it out and put it close to the the painted part so that you know how to space out the lines.
If something goes wrong, use a soft, clean brush with a small amount of clear alcohol (damp brush, not wet) to erase that line. Use the brush to take some paint off, clean the brush in alcohol, take off excess alcohol (so that the brush is damp, not wet), take some more black paint off, clean the brush again and so on.