There are two approaches you can use for the first coat. The manufacturer of the product you use may recommend one or the other, but I suggest that you experiment with both on a sample board to decide which you prefer. Venetian plaster is traditionally applied with special steel trowels that resemble wood-handled dough dividers. You should be able to find a trowel near the plaster at the store. But you can have just as much success spreading Venetian plaster with a 4- or 6-inch steel trowel that is used for applying joint compound to drywall. With the first technique, this is the only application tool you will need.

Open the can of plaster, and add the tint, if necessary. Mix the ingredients thoroughly with a stir stick. Start at a corner of the room. Scoop some plaster on the trowel and then, holding the trowel at a 20- to 30-degree angle, apply a thin coat to the surface. Continue spreading plaster while varying the length and angles of your strokes. Don't worry about covering every square millimeter evenly, as you would if you were painting. Let some of the original wall surface show through in spots. Keep the coat thin and reasonably smooth. Clean off the trowel from time to time so that you don't find yourself spreading bits of dried plaster into your finish. Let the plaster dry thoroughly before applying the next coat.

The other technique requires that you apply the first coat with a roller and a thick nap roller cover. This will produce an initial finish with more pronounced texture than the first technique. The trick is that you will need to go over the finish while still wet with a steel trowel to smooth over the peaks somewhat. This approach should prove to be quicker on large surfaces, but you need to vigilant about troweling the surface before it starts drying.