How do i tan my butt and thighs?

So I have been tanning my body and it's going pretty well. I've been using my neighborhood pool to tan and im happy with how it's coming. I tan pretty fast since I'm Italian/Puerto rican. The problem is my upper thighs and butt wont tan since I can't go nude. I'm 15 so tanning beds aren't an option. I don't really wanna spray it on because I don't like the idea of that. Is there any way you guys could think of that i could tan my booty and thighs.