I've used nail polish for years. Never had a problem. To remove a nut a q-tip with nail polish remover or acetone works great. The acetone and nail polish remover will melt ABS for just a few seconds but hardens back up quickly. If I don't want it visible I use clear nail polish. Most of the time I use a color of nail polish other than blue or red so I can distinguish it from temporary bond and permanent bond thread locked.