I had a set of battens like that.

Lightly sand them and apply a coat of water based polyurethane. Then keep your hands off off them as much as possible. Take them with you when you sell the boat.

The heat shrink tubing works. It does stiffen the batten though. A lot of the stock of heat shrink made for battens is getting old (15-20 years) and not stored properly. If you want to do this, buy new PVC or teflon heat shrink from an electronics supply store.