Turn your clothing inside out before washing it.

Only wash with cold water.

Never use a dryer but rather air dry it.

The use of sport wash (as you mentioned) or other "hunter friendly" detergents is recommended.

As for how often...that depends on how often you wear it and under what conditions. If you sweat alot in it then I would wash it often. If you only wear it while you are out hunting and not during the rider to and/or from your hunting area then I would think less often. Once a week if you only hunt a few times during the week should be a good place for you to start with.