I apply both products in sections, just to make sure that I haven't missed any areas. I try to make sure that my hair feels very slippery (with gel) but when I use mousse, I know that I've used enough when my hair begins to feel like it has "set" (ie, it feels like it has a little hold). Personally, it's impossible for mr overdo either product. I just wind up scrunching out the crunch when my hair is dry.
Curly and PROUD!!!
My hair has a mix of low/med/high porosity, and it's medium textured (some are still fine, though!)