Martyrs will help astronomically with clearing out buildup. To avoid situations like this I reccomend making occasional raids when you start to notice buildup. If a planet accumulates over ~500 ships then I go clear some out.
I typically do this. I rarely play with spirecraft (asteroid based) on, so Martyrs aren't really an option to me. One thing I'll do when this happens is pull a bait and regroup on the enemy. I'll let them build at my defensive wormhole, and then pull my fleet back. This usually gets them to engage. Immediately reverse course and handle them in my own system, preferably with turret and booster supports (Anti armor and armor x3 from zenith traders, for example).
Another trick is return the favor, if you can't get them to commit, but you need to be on particular style maps to do this (like simple). Loop the enemy and come into their system at a different wormhole, preferably with long range firepower (blade spawners, snipers, zenith bombards, zenith snipers, etc.) Once the majority of their fleet is in range, retreat back through.