One of the reasons, I think, that some people find the plastic reels more difficult then the steel reels, is that the plastic reels flex more.
If you are using the plastic reels, practice in a manner which concentrates on keeping the sides parallel. That requires a light touch, with even pressure from both hands. I think that for some people, this comes naturally.
If you can't make the plastic reels work, the steel reels have some real advantages.
You may find consideration of my circumstances (and how I've dealt with this problem) useful to consider.
As I've mentioned before on a couple of threads, I have limited strength and dexterity with my right hand. As a result, I am not able to use that hand to guide the film on to the reel, I have to use it to hold and rotate the reel, while the left hand is used to handle the film. Because of the limited dexterity in my right hand, it is difficult for me to hold the plastic reels in a manner that keeps the sides parallel - they flex slightly, and go slightly out of alignment with each other as I try to feed the film in.
The steel reels, being more rigid, don't have this problem for me. Unfortunately, the clips are another problem, because all of my 120 reels have clips that need to be activated by the hand that is not feeding the film .
I've tried to come up with a method of activating the clips, using the fingers of my left hand (the one feeding the film in) but so far have not succeeded.
From the descriptions here, it may be that the Hewes reels would be usable by me - but I don't have a source nearby that would allow me to try them out first, and they are somewhat expensive to import on spec.
By the way, I have no problem using the steel reels for 35mm, at least the ones (Nikor and imitators?) that do not have a clip, but instead a slot that the film goes into and crimps slightly, thus holding itself to the core. I think that it is the additional stiffness (relatively speaking) of the film base, and the narrower width, that makes this possible.
I am working on trying to develop the necessary feel to be able to position the 120 film on top of the clip, and to load it smoothly enough as to have it stay in place due only to the slight friction this entails, but so far have had imperfect (although improving) success.
If all else fails, I can go back to my 120/620 Kodak developing aprons, but I would prefer to use the reels.
Good luck, and keep practicing.