I was using a tablet with a cover when I started using RM. I just made a little chart with all the r/w per club, placed it inside the tablet cover and referenced the numbers while playing. IMO you'll end up using it the most with the short and long irons, so after a bit you'll just start to remember what they are. I use the hornet (1.25 max) and the backbone (1.50 max) mostly so I just remember what they are. For the mins I usually add 1, obviously the mids become .5
All just rough estimates, I've never used the app and probably never will. It's second nature now, I'm already calculating while I figure out where in the mid/max/min range the shot will be. I used tour one (who cares if you time out, you're losing 50 coins) to get more precise/timely with it until I felt ok about using it in real time.
If I was going to make a recommendation, I'd start with one club (long or short iron), get really comfortable with that and then apply that knowledge to the other clubs using each clubs r/w value.