The paint is not actually that wet for long at all. The thinner you mix the paint for blending, the quicker it dries so when first trying this technique I recommend using thicker paint. I don't use slow- dri or any other retarder as I don't like what it does to the consistency of the paint. Just ...
@IDICBeer - I hold the damp brush between my teeth and then wet the bristles between my lips right before the next blend.