I did use a golf ball a few times, but sometimes you need someone with a thumb or finger to get just the right spot.

You aren't grinding on anything with trigger point, it is finding specific spots or knots and then applying a steady pressure to that area - hopefully until it releases. Only should take 20-30 seconds, if it doesn't fade away then it is not a TrP or you aren't on the main spot for that one.
The pressure pointer website does have really good info on the User Guide page and a click able pain chart page to help locate trouble spots by symptoms.

There are active TrPs and then latent TrPs.
usually you tx the active ones first, then the latent ones may show up more, then tx them.

But I wouldn't take them on yourself so soon after surgery, I hope you can get some expert PT after the area has healed , and that they will treat any triggerpoints manually =hands on, for you, as well as massage and other pain reliving treatments.
Or perhaps a therapeutic massage practitioner that specializes in TrPs and healing, more than a focus on strengthening and such -like many PTs seem to do.