If you're having a lot of problems with pooling washes, then chances are your surface is too glossy. Try dullcoat as step #1 and apply washes on top of that. The little bit of tooth from a flat finish should keep your washes on the flat surfaces.
Not like you need more products to buy, as lots of folks here show great results with acrylics... but one reason I use oils is that they have much less surface tension, when mixed with mineral spirits, than any water based wash I've played with. They also dry a lot slower, so you can work unthinned pigment around for a long time without it drying in a tell-tale puddle.