Whatever you expect from your child, you can't hand him the rule book of life and tell him to learn it all at once. The fewer, age appropriate, major rules a child has to follow, the greater his chances of success at learning them. And once he has learned the basic rules, he's ready to further refine his behavior. Fortunately, school age children have adequate language abilities to deal with many of the less serious issues that we don't want to turn into rules. While it's obvious to you that you could avoid getting finger paint on your best clothes by changing into your work clothes, ask yourself how often you did just a little potentially messy work without changing only to regret it afterward.
Adults make mistakes that have consequences just like children do.
Children need to see the consequences of their actions. You should avoid letting your frustration turn these situations into issues of discipline when they should be learning experiences. Even when a child is too young to clean up his own mess, it's never too early to involve him in the process, and talk about the problem. Keep the conversation calm and put it in terms your child can relate to, for example, comparing damage to his clothes or your property, to damage to one of his favorite toys or possessions. Let him understand how you feel by exploring how he would feel.