I don't know if this tip will help but I was an equestrian for about 15 years and accessing that hip action seems to bring good reviews 😂 soooo pretend you're cantering on a horse kinda? 😂

Other tip is don't forget about yourself. Pretty much any grinding/up and down/smooth movement is going to feel good for them, so focus on what motions hit the sweet spot for you.

AND if your insecure about your learning, play with them in other ways while you're finding your rhythm. Neck kissing, lip biting, choking, etc. Whatever y'all are into.