I have purchased Mig's Lucky Varnish in satin as a final finish for a aircraft model which I have completed. They advise that no thinning for airbrushing is needed and that it is water based. I have had the bottle for about 6 months and it looks like there is rust forming at the base of the bottle, do they use steel balls as a agitator ? If so how will this effect the final finish. I have tried to spray the varnish on a donor spare wing and am not happy with the finish. Can anyone recommend a good Satin finish for my top coat. Thank you in advance.