Decoart. has some great paints
It depends on the material you are painting. There is a floral spray used in florist shops to color flowers, both real and silks. I am sure you could find it in some larger craft stores.
Amy: maybe these will help
Amy....I used spray paint for mine and that was several years ago but it still looks good.
I agree with the spray paint. It works well. The other thing would be to use fabric and cover them. I did that with these lamp shades using burlap. https://michellejdesigns.com/how-to-make-old-lampshades-new-with-burlap/