I use some type of industrial magic tape, 3M type of thing. About 7cm width- packing box size.
Flipped the plane inverted, deflected the surface away from the side indended to seal and ran a lenght of tape alone the hinge line, sticking to both the Stab and elevator/ wing and aileron. When you release the surface to neutral, the tape folds into the gap but doesn't stick inside the hinge line.
I did it as a quick fix years ago and it's never come off. Works great. Simple and invisable.
The bad news is that it's takes a good 15 seconds to do each surface perfectly!
Bummer ...60seconds lost.