To avoid injuries, it is sufficient to rub the glans lightly with butter. I also wash the penis and hands before and after masturbation. For me as a habitual solo masturbant, it is very important that the penis is always ready for use. I have been masturbating almost every day for 67 years and have never had problems with my penis. I still have my foreskin. Circumcision without medical indication is nonsense, I'm glad that I still have my foreskin, it is great for masturbating with it. I don't have any problems with cleanliness, because I wash the glans with the foreskin pulled back, twice a day and after use (masturbation, sex). But I can only recommend removing the frenulum preputii (frenulectomy), the advantages are: 1. The foreskin can be pulled back further, which enables a larger stroke during masturbation and the foreskin is more flexible. 2. The penis looks better because the foreskin can be pulled back almost without wrinkles. 3. The penis is much easier to keep clean. I removed the frenulum completely myself in three operations. But every urologist does that too.