Posts
Oil paint plus...
acrylics
Oil takes a long time to cure so you can paint over acrylic, but you can't paint acrylic over oil unless the oil is cured (you can use an acrylic varnish, but 3-6 months (and up to a year for thicker brush strokes) has to pass before using.
oil pastels
Oil pastels never truly dry due to their heavy wax content. So you can use them over oils but never under. I have used them as soon as the oil paint is completely dry to the touch, to good effect. Just remember that although the oil pastels do get hardened over time they will never fully cure.
Paintstiks
Paintstiks are just oil paint with a bit of wax binder...they are different than oil pastels, they just dry a lot quicker than regular oil paints. They can be used with oil paints but due to the quick drying rate they need to wait to go over the regular oil paints until it's dry.
Watercolor
Watercolors are great for a wash under any medium. The only issue is that they are water soluable, so a wet acrylic will probably lift some paint.
Charcoal/soft pastels
You can use charcoal or soft pastels as an under drawing but you should use a fixative so the paint won't mix with it. I use a spray retouch varnish.
Graphite
Pencil can be covered by just about anything, but there is a possibility that oil paint will mix with it. The best way to fix it then is to put a see through wash of gesso over the pencil before painting. You can still see your drawing but it will be fixed and have a good ground for the oils.
