Thanks a lot Mezmorized Potato. Yes this is what I've been trying to do and that was informative, with similar advice as in the video.
I read it's supposed to feel smooth on the surface, and I think my testicles both feel smooth on the surface. I thought there were some lumps behind, but I they could be the spermatic cord.
I have some kind of aching feeling sometimes in the top corner. I think it's because it's twisting sometimes maybe.