Yep.
get someone to hold the bike (leave the subframe on the bike) I have used metal pipes and also 2x4's depending on the occassion.
I had a tightly bent subframe on a trials bike once. I cut a piece of tube lengthways that fit on top of the bent one. I welded the cut piece to a rod about 12" long (it now looked like a capital "T"). I was then able to beat the kinked piece back into place without it looking like I attacked it with a claw hammer. I hope you can vision that, my description is poor.
I used a large pipe, and a piece of wood.
Due to the way the gasgas subframe is, in that there is the seat mount on it, I couldnt use the pipe to bend it back, so used a piece of wood and the pipe to line up the very end pipes on the subframe.
Its better than it was, but still not perfect