Hello - your question isn't quite clear, but I assume you mean whether to paint the parts before or after cutting them from the sprue. In general, I prefer the paint the larger parts such as bodywork after assembly so that the seams and any other defects can be covered up first. Assemble, primer, sand, filler, sand, paint is best. For the tiny parts such as handles and such, it's easier to paint on the sprue and touch up later if any of the attachment points are visible. Another option is to cut the part out, clean it up and superglue a toothpick or pin to a spot that won't be visible and use that as a handle while painting, You can stick the 'handle' into a lump of modelling clay while it dries.