I've been working on DPT with Annie in the house for a few months now. We started the public version in class a few weeks ago. I was feeling miserable and hurting, so I sat on the floor and asked her to crawl on lap and put pressure on. Ok, let's be honest, I lured her on and rewarded heavily. She thought I was a bit nuts for interrupting her normal crate routine, but it helped.I think I might start with teaching her to lie on my legs and apply pressure. She does that naturally anyway so it shouldn’t be too hard.....at least not at home. Out and about will be trickier. She’s not naturally very handler focused. The world is too exciting.
Head down, which I think you already taught helps teach this, as does crawl (I am doing this sitting on the couch/floor/bed with my legs straight), the challenge is working on duration. After we have worked at it for a while, she falls asleep on top of me, but bridging those two so she relaxes sooner without hopping off has been a challenge. She wasn't ready to commit to napping in public yet though, so probably more work on relax on the floor in public is needed before I try and get her to relax on my legs again! Still hard to do in pandemic times.
I have tried the version where the dog just puts its front legs up on a person seated in a chair and discovered Annie has very boney elbows.