@Meet such a long time ok will try making that again as i lost all my older works
1. Well the baic idea is to first make a brush of what u wanna fill inside the render
2. like i did with AB devilliers
3. So make a brush
4.Then make a new layer above the original render
5. select parts of render with pen tool and then after selecting click the new blank layer
6. Now fill the part with the bursh
7. repeat the same step again and again untill you get something like that