Don know if this will be helpful but I had an experience with a shrinking penis about 7 years ago. In my case it was brought about increasing age and related EQ issues. I had shrunk from 6 1/4” down to about 4 1/2” from memory. I started doing a few simple stretches in the shower without knowing what I was doing and stopped the decline. After that I bought an extender and discovered Thunders and got my length back and more to about 6 3/4” mainly using an extender. As well as the regained length I found the extending also improved my EQ.
My next move was to start pumping mainly to improve EQ which it did in spades. I then moved to dynamic pumping and now use a combination of a Mr Fantastic air pump and a water pump. Apart from further gains in EQ this gave me an increase in girth from 5” to 5 1/2” MSEg and I believe I am still growing girth wise but have had no further length gains.
I am uncut and like you found it difficult to do manual stretches. I found the extender approach easier once I went down the DIY velcro strap modification to get away from the dreaded noose pain you often get with extenders. This is the sort of extender I have been using https://www.ebay.com/p/Miracle-Slid…ches/1963233135 but with the DIY velcro strap. You can find links to that by searching on Thunders.
I now find my penis is easier to stretch after a pumping session and do a two hand fulcrum stretch in 4 directions. Find it complements the pumping and helps to remove any extra fluid in my foreskin at the same time.
Hope this helps in some way.