Hello I've done many plastering jobs around the house mainly skimming but I for whatever reason can never get it like a pro plasterer. I apply first coat of skim then leave it to go off abit then flatten off then apply second coat more or less straight away, leave second coat to go off a little but still workable and flatten it off filling any holes and hollows, I then go straight over it again with a wet trowel and finish with a dry troweling. Am I doing anything wrong it seems to feel chalky when fully dry leaving a little dust on my hand. Could any pro plasterers let me know what I am doing wrong. Many thanks.