I try hard not to swing, but to "pull" the leg up. I point the toe. I do a one count at the top.
I don't rest my back against the pad. Lately, I let the rear leg extend back a little (opening the angle, feels like it isolates the target hip flexor more rather than using rest of body as a lever). I have a bad shoulder, so actually work a bit on pushing up with a little bit of a shrug in the shoulder, so am not griding into my shoulder from the weight of just being on there.
I feel it somewhat in quads and stomach and arms (from being on there) as well as hip flexor. I must be the only person in the world, who is trying to isolate the hip flexor and keep the abs out of it!

Actually, as I write this up for you, wonder I should alternate L/R each rep, rather than the 11/11. I definitely feel it worse on the second set of 11, since the abs become tired (even though I am working on isolating to the hip flexor).
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Anyhow...what do you all think of this apparatus, what I'm doing etc. Interested in other people's thoughts and I will prmoise not to get defensive.
*It's almost a warmup...but I gotta watch my knees, have issues with leg press or squat if go heavy there. Anyhow...that's not the point.