I taught my dog to limp using the above Kikopup video. I found that to transition from the "held" position I had to just start touching her shoulder lightly, she is a small dog so I have to lean way over to do this. Eventually I was leaning over and just hovering my hand above her shoulder (out to the side a bit) and it became the cue for her, then I slowly transitioned to where I could stand up. Finally, I didn't want to have to lean over at all and needed to get her to do it from a distance, coming toward me. I started by having her limp one step (I was sitting on the floor and reached to touch her shoulder or act like I was going to reach to shake her paw, C/T for her raising it and then move to C/T for one limp, then 2, then 3. That's where we got stuck so far, 3 limps. For distance I toss a treat and then tell her to STOP (or stay). I put my right hand out in a STOP position, fingers splayed, then let my wrist go limp and say LIMP. That is her cue. For the other side I use my left hand. My problem is only 3 limps and she'll only do it as she gets close to me.
P.S. I remember I told her to HOLD so we could get the paw in the air longer and longer.