Speaking from no expertise but my own decades of living, the only way to do things you don’t want to do is to do them. No excuses, no procrastination, no unrelated rewards, just do it. Everything else is a hack based on procrastination, or making you feel good about procrastination. You have to make a contract with yourself, where there is no payoff but that the thing gets done, and then do not break that contract. If you can’t make yourself do big things, make yourself do small things, but do them without fail.
If you do that, you will become a different person.
> the only way to do things you don’t want to do is to do them
Do you have anything that's not tautological?
Same 'speaking from living' and I want to amplify a spark you mention: break down the task into smaller pieces; the size of the piece is how much time you can force yourself to do the task, fully knowing after 5 minutes (10 minutes, whatever) you'd have done that mini-piece. This builds success, power, confidence. Then you can tackle the NEXT piece, etc. Virtuous cycle. ("See, it wasn't THAT bad...maybe even a little fun!")
How do you eat an elephant? One bite at a time.