DRDT
I have used all three methods; C frame, DRDT and squeezer. I did not purchase my DRDT until I was working on the fuselage. I wish I had bought it when I bought my empennage kit. From my experience when handling large sheets it is easier to get consistent dimples with the DRDT. Having said that, there are / were times the pneumatic squeezer was just the right tool for dimpling.
I can not image going back to the C frame. I am sure others will disagree.