Another homer newbie question about maintenance

Hey guys,
Will be doing some bushing maintenance cleaning before spring is back and would like to know if it's best to remove the shock in order to do this properly. Speaking of removing the shock - do I need to remove all the air out of it before removal?
And how often is a good practice to take out the bushings and clean them up? Trying to lube the HL ones was not so successful in my opinion. But again, I've only ridden the Spot one season - which is short here in Eastern Canada. So for all I know there was enough grease in them and everything is fine and dandy.
So I figured I'll just "get to know my bushings better" and take them apart as a practice run.
But what about removing the shock procedure? Is there any amount of tension on the shock when it is put in place?

G