One other thing you can add if you are thinning it with a bit of water, is to add a very tiny drop of dish detergent to the mixture.

This will effectively eliminate surface tension and will tend to flow into the crevices a little cleaner.

Basically something like 10 drops of thinner, 10 drops of water, and then take your paint brush and dab just a smidge of dish detergent on the brush, stick it in your mixture and blend it all together.