I have an old jo and bokken that are quiet damaged after repeating hitting other fast flying pieces of wood. Is there a way to bring those back to life from an aesthetic point of view as they are find from a structural point of view. They just look fairly well worn.
Usually, it's enough to give a light sanding with fine grit sandpaper and a rub down with boiled linseed oil. It's important to use boiled linseed oil, as it will properly permeate the wood.
If they were meant more for decoration or a trophy after years of service, and no longer intended to be used, a light varnish will give them a beautiful luster. Typically, it's this sort of varnish that's put on inexpensive and poorly made bokken, and tends to crack and chip away after little use.
If you have mechanical dents in the wood -- not broken fibers/splintering -- there's a wood working trick you can use to raise the dents: Get an iron, put it on highest heat setting. Take a clean rag wet, but not dripping. Fold the rag so a wet corner of the rag covers the dent -- touch the iron to the rag. The idea is to flash the water into steam with that part of rag against the wood. THe steam goes into the wood a little bit and you'll be left with -- usually -- a little bump where the wood is now 'proud' (above the rest of the surface height.) Then just a touch of sanding or planing. I suggest making dents in something else and experimenting a little.
There is also a small glass rod type tool that you can find at better billiard/pool stores. It's designed to be rubbed along the pool cue to raise the dents that can occur through normal play. It will also work if the wood is already lacquered, where the steam trick (Which is quite useful) won't work on sealed wood.