A good size pot of Washable Agent allows you to add it to any colour acrylic paint to create what is described as a 'washable' coat. Mix it with your chosen colour and apply over the top of a standard coat of paint. Depending on the proportion of agent you add to the colour, the effects can get will vary. A mix of 10 - 15% agent to colour is all you need. The two uses for it which come to my mind are for a winter white finish and for the Afrika Korps sand applied over a Panzer Grey vehicle. The effects can be a bit variable depending on how much of the Washable Agent you add to the basic colour.
So, I tried this out on four small scale models to see how it worked out. I mixed some into some acrylic matt white, using Vallejo paint in this case bit it works just as well with AK Interactive colours as well as other manufacturers. The percentage was a bit of a guess rather than carefully measured if I am honest, but thankfully all worked well. I used 4 models, a Marder III, and a Panzer III in 15mm scale from Plastic Soldier Company, which had already got an overall colour of Panzer Grey, along with a Zvezda 1/100 KV1 and an Armourfast 1/72 SU-100, both of which had an overall colour of dark green.
The white paint with the washable agent was roughly brushed on to all four models and allowed to dry. I then went back to them with both some cotton buds and a couple of brushes, and using water just went to work on gently rubbing the white paint which then started to come of, and provided a suitable worn look to the vehicles. Personally I am pleased with the end result, and found it really easy to do using this new Washable Agent, bearing in mind these were quickly done as a test.. The other advantage is that if you take off too much, let it dry, paint it again, and have another go. I really like this and will use this whenever I need such a worn finish in future.
My thanks to AK Interactive, who kindly provided the sample.