I tried to do this with my first, but not much luck for me. I just didn't do it regularly enough, I guess. I'm sure it is useful if it is done right 💚 I even bought one of those inflatable balls, but I absolutely hated it 🙈 again. For others, it worked, and I read very good reviews. 💚
FTM but this one gave us enough confidence to have a go!x https://www.babycentre.co.uk/x1955/what-is-perineal-massage-and-how-is-it-done
www.imperial.nhs.uk/-/media/website/patient-information-leaflets/physiotherapy/antenatal-perineal-massage.pdf