My 2.5 year-old had HFM last month. It's awful--mainly because, like you said, there's not a whole lot you can do for them. The biggest pain for me was the quarantine; he had sores for almost 10 days, so we couldn't go to any social things, and if I took him out in public, I had to be super careful. As for the pain, our ped recommended using children's chloraseptic spray. (Or oragel, but that was harder to apply, especially to all the little sores--and can interfere with swallowing.) We used it at night (when the pain would keep him up) and right before eating, so it would numb things a little. We did a lot of ice water (the colder the better) frozen blueberries, sherbert, pudding, jello, etc. For about a week, his nutrition wasn't the greatest, but we wanted to keep him hydrated and he wasn't that hungry anyway.
There are two different opinions about contagiousness. Our doc says that when the mouth sores go away, they are no longer contagious, whereas my other son's school says they can go back to school 24 hours after the fever subsides regardless of the sores. Good luck!!