Lets not get confused here between plastering and skimming, skimming is easy, well it can be easy if the background is right. I'm self taught. Firstly I would read through as many posts on here as you can stomach, theres hundreds of excellent posts by skilled and knowledgeable tradesmen on here that will make you understand the principles of what you want to do. The easiest thing to do, IMO, is skimming onto a good flat straight plasterboard wall or ceiling (dont be afraid of ceilings, its the same job and principles, your just more likely to get gear in your hair, eye, mouth, nose and ears!) In fact it's a good idea to do the ceiling first in any room thats being completely plastered. Things get more difficult from there, a plasterboard wall thats perhaps been dabbed but the boards dont sit well with each other is a little trickier, you could apply three coats of skim rather than two to help bring it out or you could need to use bonding to get to a nice flat base. I would advise you to just have a go at plastering a flat plasterboard wall or ceiling and see how you do, always use a two coat method, don't think you'll do it in one coat, not with lots of experience and practice. remember to be patient as you'll more than likely choose a small wall or ceiling and find yourself playing around with the plaster too much. heres a rough idea of what you should be doing
1 - prep - assuming all boards are fixed and theres no flex between joints you will apply scrim tape bridging every butt join between boards and also internal corners, you can get 4" scrim which i really like for internal corners as it can be easy to catch the 2" stuff and it can pull out. apply angle beads to any external corners.
2 - prep again - make sure you havent missed any of the above and make sure that the room your working in is clean and tidy, you dont want to kick a lot of rubble of grit into your plaster
3 - apply your first coat, I like to start at a top right hand corner and work my way across and down, dont be to concerned about what it looks like, just get it all over the area, once its all on you can go back over the area and flatten out a bit, dont spend to much time on this you need to get to step 4
4 - clean your tools and buckets, brush in your corners with a wetted brush, flatten off any ridges you may have created and then make your second mix, I like the second mix to be a little bit runnier than the first
5 - your first coat should have firmed up a little by now, its hard to explain but your second mix needs to be ready by this point, it doesnt take long, then you apply the second coat as you did the first, this coat will fill any voids you may have left
6 - time to clean up again and have a cup of tea, two sugars, keeping your tools clean is as important as doing a good job
7 - the plaster should be fairly firm now, you have two choices as to how you tackle the next part, my preference is to use a spray bottle, others will use a brush, your gonna apply a little bit of water to the wall to act as a lubricant really and then your going to go over the wall, this will take care of any ridges or little divots you've left, i use a spray bottle because if your a bit keen at doing this stage the plaster may not have firmed up enough and if you flick a brush of water at the wall it will create craters in the skim. dont over do this though.
8 - once the plaster has set but is still dark you can apply another dab of water and polish it off, dont over do this bit either, well thats not true really you can do this until the cows come home if you want the wall to shine like glass and you dont want the painter to be able to paint it, i suppose it depends if you like the painter or not
Ive prob missed loads of info out but its all on here, tools you'll need, consistency of mixes, so on and so forth. Good luck. oh and always buy a stainless steel trowel.
