forget the sponge, even on one coat, if you fill out your beads and joints put on a thick enough coat and as flat as possible you can go back straight on it and flatten. i wouldnt recomend one coat to anyone, forget the sponge its for jokers who cant manage to get back on it quick enough or put too much on and rely on rubbin up with a sponge set plaster and playin with the fat (dead plaster) if you do this method it will go pearshaped eventually. Ive seen it done on site 2 coat s**t, one coat s**t but have seen one and two coat spot on. Ive one coated on site if the prices are shite and the rest of the lads are shite and to be honest you couldnt tell the difference and thats on boards. forget one coatin on pva and skim, i wouldnt normaly mention one coat because lads and lasses who have been plasterin 5 mins might try it but too late i said it.lol