Yeah, I found it really difficult to relax my shoulder muscles while pulling with my arms, and that caused me quite a bit of pain initially. I found the princess grip worked far better for me than the double cupped grip and once I had that sorted it was a lot better for me. Experiment with a couple of grips and see if you have any preference. I’ve found shoulder mount grips to be such a personal preference. My instructor learnt shoulder mounds using chinese forward grip and that one scares the life out of me. Same with the grip I use, some of my friends think it feels so weird and they don’t like it.

"Prances" are a good way to prep for shoulder mount, but please take it slowly and when you think you are ready try it from sitting on the floor with plenty of mats and preferably a spotter too.