Personally ...
I generally use laquer for clear coating , then my wash is made from oil paint and enamil thinner ( i use floquil) .
That way you can put a blob of oil on the top of a mixing cup , and change the density on the fly. Oil paint is somewhat expensive , however if you take care of it , you will only need 1 tube in your life time .
Oh and now you know how i make cool looking oil leaks