Wash as much dirt off as you can first. I use a 50/50 mix of warm water and lemon juice and have had good results, an over-night soaking should show some label.Thanks for the feedback y'all!! And @hemi, do you soak em in lemon juice, or just use it on a brush?
Yes to both questions, you want to be checking on them fairly regularly to avoid losing too much of the paint.So is there any situation where the citric acid start affecting the paint,or is it possible to soak too long?