I used venetian plaster on my bathroom walls a few years ago. Loved it! I prefer to trowel on my paint rather than have it drip and splatter off my brush and roller. It's a workout, but worth it.
Basically, you buy venetian plaster from one of the big box stores. It comes tinted. You trowel on 2 or 3 thin coats, then sand it with fine sand paper, burnish it with your trowel and wax it with carnuba car wax.
It's a little pricey and you have to buy a full can of paint in one particular color. Can there be a cheaper way for you to make your own in a variety of colors? I looked all over the web and couldn't find a recipe so I thought I'd try just mixing marble dust into paint. Will it work?
First of all, buy marble dust. It is available here. Mix it into any latex or acrylic paint; 50% paint and 50% dust. I use a pyrex pie plate as my pallet and mix with a plastic putty knife until all of the dust is incorporated and the mixture has the consistency of tooth paste.
I think it's best to apply this to a rigid surface such as wood but experiment with other grounds to see what happens.
Trowel on the first thin coat in a criss cross pattern. Lightly sand to remove any ridges when this coat is dry. Trowel on your second in the same manner. This time scrape off as much plaster as you can. This leaves an almost transparent coat. Repeat if necessary.
Lightly sand with fine sand paper.
You can stop there, or add another color. Place a stencil on the wood tile, mix another color (with marble dust) and trowel it over the stencil. Remove the stencil before the paint has dried. Some of the second color may bleed under the stencil but you can remove it with a wet Qtip or wait until it is dry and scrape it off.
Lightly sand again and then burnish with the plastic trowel. Rub on some carnuba car wax, then buff off.
If you didn't know better, you would swear this was marble; smooth, cool and fabulous.