Easiest way to limit wiping is to constrain the field size. People are much less likely to wipe if there are other people around possibly watching them.
Marking the boundaries is really how much effort you want to put into it. You really can't be overly clear. But if you only Mark a few trees here and there it is easy to loose track of the boundary when you are in a firefight and accidentally cross it.
I ran a paintball program for a camp a long time ago. We just got some "flagging tape" it is not a long term solution but at around $2 for 300feet even if you have to re run it every once in a while it's a cheap and visually clear solution
Just go tree to tree to tree, wrap it around each tree and it makes a super easy to see boundary
Depending in the size of your field, I used around 2000 feet for my initial run.
Make sure to create a long corridor (marked with tape) between the play field and your staying area