We recently bought a house and one of the bedrooms is a disaster. The previous tenants let thier daughter splash black paint over the purple walls. The paint is thick in most spots and is still a bit soft. It balls up when sanded. What can I do? Was thinking about trying to do a knockdown finish over top, but not sure if that will work. Not so much worried about killing the color as i am with getting an acceptable texture. Flat would be great, but knockdown would be an acceptable compromise. Thanks for your help.