Cold water tolerance

It started today. Walking around in high 40s in only shirt-sleeves. (I mean, yes, I had pants on, too. Don't get me wrong.) Several years ago in prep for my second attempt at a crossing, I would start my cold water tolerance not even in the water, but walking in temperatures that others would consider cold, but without a jacket. See, I had failed my previous attempt (2015) in 55-57F water after 2.5 hours and almost 5k. I didn't want that to happen again. At that time, I had no ready-access to OW to practice in, and pools there (former Soviet Union) were way too hot. So I did a few things. One was being improperly clothed for the temperature and the other was to end every shower with slowly lowering the temp of the water. It apparently worked as I succeeded in my next attempt. The water was a bit warmer (64F) but I never felt cold for the 6+ hours I was horizontal. Now I'm lucky to be near OW. Been traveling lately, but am planning to go to test the water this coming weekend. Coldest I've ever done was last Halloween, 51F, and that was only standing mid-thigh for 10 minutes, then jumping in, stroking maybe 8-10 times, then turning around and walking out. This year I intend on starting early and continuing for as long as I can. What sort of things do you do for cold water tolerance if you a) have no ready-access to OW and b) if you do?