Mainly most surfaces can be painted, the key is always good preparation and the use of the correct products. I’m sorry I’m not a fan of the “shabby chic” look in my opinion its just a poor excuse to half paint something and get away with it when it wears off quickly.
Yes I’m aware that done correctly, with a base colour, followed contrasting top colour systematically “worn back” to create the desired effect you can seal the whole thing in with either a wax coat or simply varnish, but it still doesn’t impress me sorry.
We have done several items of furniture over the years both for customers and some more adventurous items for Ideal home shows or Grand Design live exhibitions, the process is basically the same. Wash of any contaminates, abrade surface to remove defects, old runs or sags wont look good on your newly painted chair legs.
Do any minor repairs, tighten legs or table tops fill any minor holes or cracks that have appeared with age. At this point it depends on the item your painting, some may require a good adhesion promoting primer to allow your paint to adhere properly. If its a factory finished item or laminated surface I would recommend this certainly.
Then finish with two or three coats of your favorite paint, current trends go towards various chalk paints at the moment such as Annie Sloan or Rustolem. Which these can create a pleasing finish to the eye and occasional touch, if used for higher traffic items I’d recommend a finishing wax on top at least. Or perhaps paint the item in a modern water based eggshell finish which will give you more durability providing your substrate has been prepared correctly.