Practice how you play. If you plan on wearing armor in real time than an intro class is good place to start. I wouldn’t wear it for the full class though. Depending on your level of fitness I would try to wear it for half the day. It does get rather tiring and cumbersome after that. And yes, will become a distraction. You’ll learn there’s a big difference shooting prone with or without body armor for example. Also try and have someone video you as you draw your pistol from your holster and conduct reloads. It’s a great way to see what’s working and not working. If you like pouches in certain locations etc. Years back I took a Paul Howe class and he videoed everyone on the draw and pistol manipulations. Was very beneficial.