When gluing those small pieces inside a tight space, the only clamp that you can use ( your fingers) will most likely end up being glued to the piece better than the piece is glued to the airplane! So what I have been doing is applying a very thin layer of Petroleum Jelly to the finger tips I am going to use to set and clamp the piece in place. Being extremely careful not to get any of it on the gluing surfaces.

When I'm sure the glue is set, I can remove my hand without leaving any DNA behind or ripping the piece back out.