I will examinee the pep to locate a piece with no tabs. That means that the tab are on the other pieces. I will then glue everything up leaving that last piece ofr the end.
For example, when I did the Halo 3 fragmentation grenade, I glued the round piece at the top as the last one. The "trigger" goes on op so it's not too bad if the glue isn't that great. Gor the "trigger" part, I glued the square piece on one of the sides last. That allowed me to slip my finger inside to be able to apply sufficient pressure on the other pieces. For the pieces that I glue last, I try to score my tab less so the paper actually provides the pressure to the tab. Right now, it works pretty well. I guess I have to come up with pictures but I don't have a digitaal camera so you will have to be patient.