Merry Christmas I love ghsp!
as for the tip…thin the paint very well. Use an oven thermometer to ensure your oven is 265. Do not bake until you are happy with what you see. Check for pooling of paint before you bake each layer. If you use matte varnish you will need to bake it for 12 minutes and sometimes a bit longer. I have found rather than risk the longer bake of 12 minutes I put it for the usual 8 minutes let it cool and then rebake for another 8. Some vinyls are too soft and do not like the prolong exposure to heat.