I've tried most of the obvious methods, with varying degrees of success.
One month I had to put a roll of microbore onto a hose reel, absolute ball ache and took ages. Hurt my arms doing it, trying to unwind it a few metres at a time then wind it onto the reel. I thought there must be a better way to do this.
So, a few months later I had to replace that hose (a JCB had driven over it and split it), plus I had to put some on 2 other reels as well.
I ordered a PIPE DECOILER. Quite expensive, £125, but oh my goodness, it worked so perfectly. It's supposed to be for laying underfloor heating pipe.
You simply place the new hose on the top, and then wind onto the new reel. Effortless, takes about 20 mins, including set up time. The thing dismantles so it fits in a box on the shelf when not in use.
This is the one I bought
https://www.ebay.co.uk/itm/193480582355This is how its used:
https://youtu.be/nk4laDn4NbYHighly recommend.