I'm just starting out as well but I've had a lot of nail bitters and I'm one as well but not like these people. What I do if the nails are really short and swollen, cut the form if I have to, then I leave some skin at the free edge but put the form tight towards the free edge so it doesn't move but not too tight it hurts. This usually works and gives me a nice surface to work on, the gel won't stick to skin I take an orange wood stick and go under the nail after so they don't do it (nail bitters find any excuse to pick at their nails so I try to not give them a reason to) even when building out on a nail bitter I have to remember I can't just make it any length the client wants. I think it's called onychophagy when nails have been bitten enough to be deformed and if there is no free edge they shouldn't be much longer than the end of their fingertip. If they insist I just explain that because they are a nail bitter the strength just isn't there and it's more likely to break off. Okay one more if the forms still aren't working for you, you could build without forms first so it's long enough for you to work with, you can then place a form(I haven't had to used fiberglass but if they need more strength and you use it you could place a small piece to bridge between the free edge and the form and continue with the resin) anyways I hope that all makes sense couldn't think of the words for parts lol hope it helps!