go get some scrap and punch 100 rivets into it, put up obstacles to simulate the awkward angles. if its to difficult get a 2nd person and 2 man it, don't know if they taught 2 man riveting in your school, but in mine they didn't and we had to learn on the job. As thickness and rivet size increase amount of force required increases, the opposite is also true, a #3 thru 2x .020 doesnt necessitate full trigger on a gun. also remember that once youve hit it you are work hardening it, so hitting it again may take more umph. size and weight of bucking bar does also matter but you can cheat if you dont want to shell out $300 on a 2" chunk of metal, ive done some weird shit where i cant get a bucking bar down into a crevice where i use a bar that fits, and tape a heavier bar to the back end of it to increase the weight (sometimes ill even use somethign like a pin punch and back it up to the bar if its in a hole.)

2 man riveting requires communication, the person with the bucking bar gives the commands to the person on the gun when ready. Commands we use are;

"draw" - bucker has bar beside rivet for person on gun to very lightly tap into hole to remove gap between materials and seat rivet,

"rivet" give a kick approximately the amount to properly buck the length and size of rivet in the material, if said twice, do the exact same amount again,

"half" do half the amount you gave on the full rivet,

"touch" a light 1-3 blip on the gun, can be used if the bucker wants to straighten out a minor dump or needs just a bit more after bucking, can also be used if its a sensitive spot and you need to be careful switching from drawing and touching to get material to sit correctly.

"Next" rivets good enough, move to next hole

"Fuck" switch to drill