I was just about to ask a question about this myself.
I've probably done around 30, 8x4 sheets worth with this technique so far.
For the edges, cut back with 120 or 180 and a block then ease the edges, the rest of the face, straight on with quick-drying woodprimer (ScrewFix) or MDF primer (Toolstation), normaly I apply two coats of this with a gloss roller, then 'rub' back with 120 grit on an orbital sander till it feels smooth, except the edges which I do my hand. From there, Leyland oilbased eggshell, ideally three coats with the same cut back inbetween but two can get you through, again with a gloss mini-roller.
The finish is well, eggshell, not matt and not gloss, quite a pleasing in-between which isn't amazing, but it's plenty good enough for me and I'm the first to pick holes in things.
My reasons for this technique are based on a few things:
1) It's cheap, primer is about £5/litre and top coat is £6/litre.
2) Mini-rollers can be wrapped in a bag after use till the next round of coats, I'll use two rollers for an entire build normally, one primer and one gloss.
3) Spray kit is expensive, but I'd gladly buy it, if I thought that a spray booth would be anything less than a total pain in the buttocks given I have a packed single garage and a bit of driveway to work in.
4) You can touch-up when all assembled with a roller again quite easily.
However, this is the root of my question, the gloss has a 24hr dry which is a total pain given how fast you can work with MDF, the primer is touch dry in 30mins normally and you can overcoat in an hour or two. What can I use as an alternative to the oilbased eggshell?
My normal practice is to fill the garage with panels at the end of the day, work from back to front painting as I go then shut the door leaving them. However, 10pm to 9am the next day isn't 24hrs and the paint's still not dry the next day if I am able to work on it then, such as at the weekend. Any ideas?
Aidan