If at all possible, I would avoid using sedatives or tranquilizers for something like clipping nails. Frequent use of those just isn't healthy for the cat.
My cat gets all worked up about clipping nails too. I've never cut too far, yet she howls as if I'm amputating a toe with every snip.
I haven't had to resort to the towel trick yet, but that is effective if you can get the towel around them snugly enough.
The cat has conveniently hidden at the very thought of this thread, so I can't grab her at the moment to verify my technique for holding her. While much of it is a "whatever works" approach, I *think* I usually have her sitting on my lap, back against my chest, and paws pointing away from me. I can then get my left arm around her chest, tucked under her left leg leg (right up under her "armpit") so she can't really do much with that one, and hold the right front paw by reaching around her...I don't worry so much about her kicking her hind legs...if I stretch her out enough, she can't do any damage with them. So, that gets paw #1. To get the other front paw, since I can't operate the clippers left-handed, I reach the hand with clippers under her right armpit, and hold her left paw with my left hand. Sometimes I have to reposition after every couple claws as she wriggles around. The hind legs are usually more of a challenge, because she's also determined to escape being held still by then. I think I just become some sort of contortionist tucking her head under my arm, getting my elbow around her front paws, and hanging on for dear life to the hind paws. You can hold on pretty tight without hurting the cat. Then again, my cat doesn't really go for blood when I'm trimming claws, she's just focused on wiggling free because she doesn't like staying still.
Something that can make it a bit easier with time is to play with their paws and hold them the way you would to trim their claws, but without actually trimming. I do that with Ember so she doesn't associate having her paws messed with only with having claws trimmed. I also will play with her ears and open her mouth from time to time so none of this is overly strange when she visits the vet either.