PLASTERING TIPS FOR NON PLASTERERS
Many trades (excluding plasterers here) and DIY enthusiasts try to get the new plaster coat smooth straight away. No need. Just get the wet stuff on the wall first.
Once you’ve successfully covered the area to be skimmed, leave it for a while, go and have a cup of tea, then come back in 5 or 10 minutes. Plaster needs time to go off, and if you play around with it too much now you’ll interfere with the curing process and end up with a streaky mess. After your tea break, go over the wall with your trowel, ONCE. Leave it again for a few minutes and then lay in a second coat. This coat will be slightly thinner than the first. Once you’ve got it on, leave it for a while. After your second cup of tea you can go back and run your trowel over it again. From here on it you can give the wall a once over, have a brew, give it another, have a brew. Repeat this until it’s nice and smooth. You’ll need to add a bit of water to the wall towards the last few trowels to keep the it running smoothly.
If you have marks and rough patches when you’re done, don’t worry. You can rub it down with very fine sand paper.
I once spent 2 hours with an industrial sander rubbing down a room the labourer had voluntarily skimmed, apparently with a fork. The finish was absolutely fine once painted, luckily.
So the take home message here is; whatever you do, don’t play with it too much.