I've seen several techniques. Rubber hammers. Nylon covered pliers. Just cutting the lip off with a Dremel tool. Clamper robot from Futurama.
Lee Oskars and Seydels that I've tried have combs that bow down in the middle so that when you screw the ends down the bow applies pressure to the middle, giving you a better seal.
SP 20's have little tabs at the end of fold on each end of the coverplate. I just bend those back with the rest of it. SP 20's have alot more screws than LO's though. I use a hammer and put a thick piece of paper on the end of my bench. It works real well. Its easy to do and nice neat opening with no marks.
