I would like to use some silk velvet to paint. Are there any special things I should be aware of?

You can certainly get some lovely rich, sumptuous results using silk velvet, which makes great cushions (especially when piping and tassels are added to the edges of the completed cushion). You cannot use gutta on silk velvet as the velvet is too thick for the gutta to penetrate, so you are left with patterns created by how you position your dies. Salt will not have much of an effect either. The silk will absorb a lot of dye which is best applied using a foam brush.