Glute Ham raises

[Ish]

I need some help with these. I don't think I'm doing them properly. My partner holds my feet and I slowly lower my body down. Then I push myself back up while pulling with my hams and glutes. We don't have the machine though, so I'm trying these from the floor. Anyone got a video? My partner is the one who really doesn't think they work right because he's 285 and the movement feels really akward for him. Any ideas, or just keep trying until they work right.

Oh, substituting in pull throughs for reverse hypers? We have the hyper little chair where your thighs are on a pad and you lower your upper body and come back up, but not the reverse hyper machine. Any ideas on what I can do here?

Thanks.