With the chickens I've had since hatchlings I've never had to trim their nails. I did get 10 hens from a factory egg farm situation and I had to trim their nails. I just held them with one arm and used dog nail trimmers to cut the nail back. Not too far, don't want to hit the quick. If your hens aren't super docile I would definitely get a second person to help you!!
I cut some of my chickens nails with a Miller's Forge nail trimmer. I also use the trimmers to blunt the spurs of my one little bantam rooster that decides to attack every once and awhile. Take little pieces off at a time, that way you don't hit the quick, if you do hit the quick a little dab in cornstarch should stop the bleeding. Good luck.
You want to be very careful not to take too much off...better to take smaller pieces over a long period of time. If the nails are clear, you can see the quick (the blood vessel)...obviously don't get too close to that. As you trim the nails back over a period of time, the quick will move back as well. My barred rock with the really long nails took two clippings about a month apart...and worked really well and no blood. I'd have some kwikstop (blood coagulant) or corn starch on hand just in case you do hit the quick.
I've never trimmed my chickens, but I have had parrots that needed trimmed. Try "toweling" them. Loosely wrap them it a towel with their feet poking out. The darkness and immobility makes them lay pretty calm and makes it much easier