Hi Matt
a mixture of approaches above, which is what i'd expect to be honest, as everyone has their own way and their own pace and expectations from this type of job.
however, John is spot on with keeping the speed down low, and if you've bought the machine i think you have, speed 1-6 is it? then somewhere around 2 for applying and spreading the compound, work it, and then up to 2-3 for taking it off.
G3, or the newer version G3 ultra, is designed to be used dry, or at the very most a slightly damp mop, not wet panels or work. A medium or even a hard mop is the right choice, but a soft mop will barely touch bad paintwork without working it hard.
used on wet panels you will simply lose all the compound up yourself and anything within 5 metres of the mop head, and you'll barely clean the panel let alone polish it!
if you've got any very poor area's of paint, then it might be safer to give the paint or lacquer a wet 1500/2000 papering first to take the worst of the high spots off quickly and easily, and save you the risk of overworking and area with the mop generating too much heat, and cocking it up!
work in small area's at a time, think of a panel such as a wing or a door, divided into 3 or even 4 areas to do one by one. Spread G3 too thinly and you'll be there forever wioth little improvement.
G3 is designed to be worked off, i.e. you continue to work it until you see the gloss of the work beneath coming through as the compound dissappears. You shouldn't have a lot if residue to buff off with a rag if you've worked the polish properly and on a small enough area.
To reinforce some of the above points, watch your edges, best to steer clear altogether except for the very lightest of brushes up to it, or even just finish edges lightly by hand.
Working, and heating the piece is a fine balance. It actually requires some heat to soften the very outer surface enough to blend it into a smooth finish, thats what polishing actually does aswell as removing the highest points of paints and lacquer, which is also why too wet, will keep it too cool, and you'll be polishing the fuel flap all day with little effect!
and finally, its hard work!
chose an average kinda day to do it, not too hot or in direct sunlight if you can help it, you'll just end up using more compound and its bloody hard work at times!
best do your yoga classes the week before, plenty of pre stretching, and live on cereal bars for that day,
you'll never reach below the kick strips after a full english to kick start the day off!
or is that just me?
make sure you let us see some before and after shots Matt, of the car of course, not any injuries sustained or how much weight loss!
ocd to another unaverse 
- but they confirmed through the chassis number its paint code 210.