Yes, I mainly try to use an Overlay layer to add the colours. Usually after going over the flattened image with a Colour balance Or if it doesn't seem to work fully or properly I might add in a color layer or change the values manually (or whatever works)
Yea. It's a bit more steps than brushing with a colour (on normal layer) right away. When adding colour, I used to do it with just a color layer. But with the overlay layer you can fine tune the values as well In the end I guess I'm just playing around a lot with different things to see what works and not.