Get a tradesman, i do such work as part of my building service and if you are not quick enough the plaster will start to go hard before you get a nice finish.if you have done very little skimming, you could be digging your self into a expensive deep hole.If a plasterer has to make good for you , he will proberly charge a bit more to teach you a lesson.Sorry if it sounds a bit harsh but no decent tradesman likes to make good. There is nothing worse than having to put right a poor job.
Remember if you give it a go, it will be very hard work and muscles will hurt which you did'nt know you had.
Best of luck :D
I have just got my foot in the plastering door, my advice would be to leave the large ceiling to an expert and practice on some smaller walls. You will just get frustrated and end up paying someone to finish/make good... I have successfully turned my hands to lots of things in the past(like many others) but plastering NEEDS lots and lots of practice...there is nothing worse than getting a third way through a first coat then realizing you have bitten more than you can chew...very demoralizing...
Hope you get it sorted...
If you do attempt it make sure you do not have any dangerous items of clothing belts/tie/shoe laces/scarf...anything that can hold your weight....just in case you get the urge to jump...:wink:
If you have done any skimming before and feel confident of getting a good finish as long as the "chunks" are managable, then you can buy top coat stop beads which are fixed to the surface and plastered up to. These give a definitive end to an area and this area can be divided up into sections of the size you want.