How many layers of plaster before Artexing?

i would fill and tape if this is a new gyproc surface, easifill 45 min, just do joints and screw holes then its ready to pva to seal to artex, 2 coats of easifill, could be done in morn and ready to seal by afternoon, no need for plastering ( mud ), much cheaper quicker and less chance of uneven surface cracks etc. generally decorators fill and tape aswell as plasterers, much quicker cleaner and generally cheaper, ie all new build are ames taped reason is because its gyproc sheeting so if its replaced even on ancient buildings it should be ames taped imo. also plaster builds out surface, so if theres coving it takes all or most of profile from edge as even skim coat should be 2 mm per coat minimum, skirting and facing same deal.

Two Layers as normal before you artex the decorators I have worked alongside before have requested i do two coats as normal hope this helps kind regards Andy

If you are replacing the ceilings with plasterboard, then you don't need to plaster before Artexing. I have Artexed for many years. All you need to do is tape the joints with easi fill, Calk the joints when dry with Artex, and then apply the Artex for your pattern.