Beginners Body Work

The underside paint is in good shape but does need a little work. I think there is two paint jobs on the car, the gold you see and I saw blue underneath some peeling paint on top. I will putting an epoxy primer on like you guys recommend. Ill just have to wait on working on the hood because I do not have my own personally compressor and I dont have a spray gun, etc. I was hoping to strip it and be able to spray it with a spray can primer before I made this discussion. So im going to wait and do it the right way. I do have a DA Sander.

Do you need to sand the epoxy primer before putting the body filler on? I have read both, you must or you don't have to depending on the product you use.