Congrats on the new handguns! The .44 Magnum is probably my favorite cartridge, outside of the .22 LR. Like .22 LRs, I feel one can never have enough .44s.
I've never loaded mine super light, but for more moderate, 1,000-1,200-FPS, loads, I've used a lot of Unique. The problem with Unique is that it will sometimes "bridge" in some powder measures, which gives one case that's about four grains light on powder and then the next one will be about four grains too heavy. This is a disastrous situation if you seat a bullet without catching it. You can help protect from this by closely checking powder levels before seating bullets or better yet, weighing all charges.
For sub-1000 fps loads, I've used some Red Dot and Winchester 231/Hodgdon HP-38, both of which worked well, but you have to be REALLY careful not to double charge a case with these powders because they don't fill the case well. When I was a young guy, I saved up and found a like-new 3-screw Super Blackhawk. My friend, who was a new handloader, picked my gun up off the bench and stuffed his handloads in it, and proceeded to blow the cylinder and top strap off the gun with a double charge of fast burning powder.
For these reasons, I've mostly eliminated using Unique and many other powders and have switched most of my mid-range .44 loads to Power Pistol, which performs similarly to Unique but without the bridging issue. It also fills the cases decently, though, I still weigh charges and do a visual check.
My other advice in addition to your plan of practicing with reduced loads is if you don't have one, get a .22 pistol to practice with in between shooting .44s, which can help alleviate any flinch you may be developing as you learn to shoot .44s. I really love .22 revolvers and semi-autos. An excellent .22 revolver for a low price is the Ruger Wrangler.
