Texture paint on loose parts I'm using Blender 2.8.

I have a mesh/model with different loose parts (joined models) in it. When I go to texture paint, I can't paint on the loose parts except of one. I can paint fine on the flat image with the unwrapped faces but not on the model. I guess I can union boolean all the parts together but it's not the effects I want when animating.

Any tips? Thanks.
Your joined meshes probably have separate materials that do not share the same image texture and UV map. You will need to make sure that they all have the same UV Map and Image texture so that you can paint across all of the parts despite them possibly having different materials.