Going slow or slower, you would feel every little response and she felt the bulging/swelling when about to orgasm. That was one thing that drove a fwb crazy. But everyone is different
My wife gave a lot of hand jobs in college when she didn't want to fuck a guy or when she was on her period and wouldn't have sex. She gave me many because I would not fuck her until our wedding night. I still remember the first one she gave me. It was fantastic. She had been practicing on others and was quite good. She said she enjoyed giving hand jobs and watching the men respond.