After a slow, easy start, you can use flexible inserts to heighten the joy of masturbating.
A few months ago I found a web page on 'sounds,' penis inserts and plugs. I was curious and inserted a plastic thermometer, about 1/8' dia, into my urethra, with KY jelly to lube it well. It felt kind of good; I started to get an erection. So then I used a flexible novelty pencil in a long, narrow balloon (as a 'condom'). That went well and I have since, slowly, worked up to using those plastic fishing worms that are somewhat firm, yet flexible, and am able to insert the really fat ones now. The sensation is incredible!
Often I leave a 12' long fat one inserted halfway while I walk around the house, or shower, etc., and the sensation of it swinging about the head gets the pre-cum going.
Anyway, I masturbate a little to get a partial erection, then lube up a clean plastic worm, (or snake!) and slowly push it into the end hole of my penis. Then I watch myself on video camera feed and jack it!
I can feel the flexible worm through the underside of my penis as I stroke, and it feels incredible!
Just as I am about to blow, the worm usually shoots out of my penis and then I climax and the worm is followed by a rocket of sperm! I sometimes watch the video of it during the next round.
I like this so much that sometimes I leave a fat worm (I'm up to 1/2' dia!) in my penis all day, except when I pull it out to pee, and jack as soon as I get home.
I just make sure that everything is very clean and proceed slowly with the insertions.