I have found over the years that there is more than one way to skin a cat, what I mean by this is there are lots of different but perfectly acceptable ways of plastering so my advice is listen,watch and learn and to try things out for yourself, do what ever you find most comfortable but also leaves a good job.
I have skimmed over 100's of metres of artex and have found the best method to be:
1: Scrape the high spots off
2: p.v.a the ceiling to help kill suction (Gauge this yourself IE is it painted ?? what paint ?? etc etc)
3: Lay up a nice thick coat of plaster (I use multi)
4: Trowel a few times until nice and firm
5: Lay up another fresh coat of multi
6: Trowel until your happy
If the artex is super heavy then you might need to give it 3 coats but for 99% of jobs 2 heavy coats is plenty.
i prefer to board over, by the time you have scrapped the high spots then pvaed it all making sure not to miss one bit then pvaing again and hoping its not artexed on paper or the joints havent been taped or a couple of boards havent dropped or the nails havent popped and the paints not loose or its silk paint maybe distemper i would have it boarded it offering strength to the ceiling extra fire and sound protection and alot cleaner and the same cost if not cheaper when you add up the man hours and also the revisit when if falls down or cracks cos pva failed.
So, there you go, more than one way to skin a cat..
as for my bit I'll mention that just occasionally the pattern doesnt really offer up high spots to scrape off and the stuff is painted with gloss paint..
you got a couple of choices...
bonding (apply wba or thistle bondit first NOT pva) then 2 coat skim..
or thistle bondit, thick 1st coat, top as normal...
or if its a ceiling... overboard it..
So if you really are a beginner and youve got an artex surface... just be a bit careful
or having read this, you might wanna get an experienced spread in.. :-X
I agree there is more than one way to skin a cat ....but..one thing non of u boys mensioned which i think is very important.......why havnt u re screwed your boards that are up thereback up... if you are laying more weight on an artex ceiling why not re screw it..this surley is fundamental in a reskim on artex....cracks can easily appear because of this extra weight, beacuse the boards were tacked up, because the artex didnt seal background properly and tape properly...all these can cause cracks on board joins.....but im with flynnyman i try and convince them for a reboard....laying on artex can sometimes cause problems and if u guarantee your work not re-screwing your just begging for problems, it might not happen on 70% of these jobs but cracks will appear on 30 ish if u dont re-screw old boards....some will disagree on this...but due to a few call backs over time i ~ALWAYS re-screw old boards on artex reskims...sorry to sound a dik...but this is true )....its still a job for a beginner..if they cant locate a joist and reboard in my opinion they either need to learn the trade properly / get them selves on a DECENT plastering course...after all re boarding a ceiling is pretty basic stuff that all newbies should/ have to learn...due tp distemper etc as mensioned above
I should have mentioned that as 95% of the time I re screw the ceiling, I find the joists chalk line them through and Ive got a collated gun so it only takes 10 mins to do.
This is well worth doing like phippsy333 says most ceilings back in the day were nailed up and are now starting to sag, I to have been called back on a few jobs where cracks have appeared due to the extra weight.