I have a model that is complex in structure, when I tried to use smart uv project and started painting with textures, the paint started appearing on other parts of the object due to bad uv. Disabling backface culling doesn’t help much. How to make a good uv for this model?
Ok, dude - seriously… a significant part of the problem starts with the fact that the mesh looks like garbage. Every single thing you try to do that depends on polys and vertices is going to be a PITA, at every step, unless you clean up the topology.
(I’m not even sure how much “cleanup” is really an option. I’d just throw the whole thing away and start modeling properly.)