My way is to unroll carefully until you can feel the film, then hold the film only and let the rest hang down - I usually leave it (the paper backing etc) on while I get the film on the spiral as it gives a little weight and helps (a bit) with the curl of the film. You can pull it on a half reel manually before beginning to wind with the spiral. When I get to the end I just tear the rubbish off, which you can do easily without scissors.
Once you're used to it, I find 120 mm easier than 35mm - less fiddly, shorter film, and you don't have to get it out of the cannister....Good luck
You've been told all the secrets but one: load in complete darkness (I, too, use a changing bag), separate the film from the paper (I pull the tape carefully off the paper and fold it over the end of the film), and load carefully. If you use a small nail clipper to cut the corners off the leading edge, it loads on the reel much more easily because the corners do not catch.
I use the Jobo plastic reels and this system works well for me. I've not yet cut off a finger with the clippers in the changing bag, and it does make the feed of the film from the outside very easy.
It is a good idea to pull the backing paper of the film gently as the marking tape can produce quite impressive static sparks.
If you roll the film separate from the paper backing you can hold the film end eith the tape in one hand and tear the tape at the end. This way it's not pulled off the film or the paper.
I've no idea if tearing the tape itself might cause a spark because I'm working in a changing bag on the dining room table. But, I tear slowly and have not seen any problems in my film.
On the subject of loading two rolls of film on a single spool, I've not done this with the Jobo 1501 reels, but i have with the 2500-series spools. They even come with a plastic stop so the second strip doesn't roll over the first one. A couple of weeks ago, I did this with a large drum and processed six rolls at the same time. That helped me catch up on developing. :-)
I've always had the best luck with rolling paper and film into 2 rolls, the film will naturally roll smaller, it almost does it automatically. When I get to the end (beginning of the roll) then I slowly peel the tape, no static marks yet. (maybe a few 15 or so years ago when I was more impatient...)
When I used to use stainless steel reels I always left the tape on and loaded from the taped end. The SS reels load from the inside out and the tape helped the wire clip get a better hold on the film. Never had a contamination problem from the tape. Now I use Jobo plastic and remove the tape - they load from the outside in. Also never had a problem from the 'spark' damaging actual frames on the film.
"I always take a camera, That way I never have to say 'Gee, look at that - I wish I had a camera'" -Joe Clark, H.B.S.S.