this is a plasterers forum full of plasterers how many times do you go over a wall? a perfect job can easily be done by a tradesman with min of water and min of trowel ups
the first thing you are learned as a plasterer is never polish your walls its not needed (it only feels good and sometimes looks good) but painters dont like polished walls or they never used to years ago
its just time wasting, the time it takes to polish a 30m room you could have had an extra 8m wall on, if you are skimming 3x 30m rooms 90m per day thats an extra 24m complete you could have if your not polishing for the same amount of energy used, and at £2.50/£3.00 per m thats £60/£70 extra a day between you and your labourer
new work --1 coat knauf no lay in --- 2 trowels finished perfect job, very rarely 3 if you catch it wrong/' 30m/35m batch
new work -- 1 coat multi BG finish --1 lay in --1 sponge --1 trowel , sometimes 2 if you catch it wrong, 25m/30m batch perfect job
old work-- 1coat and 1 layin or, 2 coats if bad walls useing multi-BG- 1 sponge, 1 or 2 trowels, perfect job 15/20m batch