One trick for releasing the halyard slowly when the clutch is at the cockpit and you are at the mast is to stand on the exposed halyard routed on the cabin deck. You could even install a cam cleat on the mast which holds the halyard there to make this easier. Harken has that recommendation here for the spinnaker halyard, but it would also work for the main:
The other is to flake it well at the mast (making sure to get the alternating flakes there), then fix it up at the far end of the boom from the cockpit. When I'm singlehanding it is hard to flake it properly at both ends by myself, but if I do the mast side first then it goes easily.
If you find it hard locating the right flake points at the far end then you could get them right once and mark them to make it easier to find them the next time.