Actually, many LFS in my area do we sell stuff that kick-starts it... I don't know how it works, but it says it does!
I think you should add in some water from a cycled tank, and use the filter media from the other tank if you have one that matches then replace that one. If not, float your filter media in that tank for a week or so, then put it into the 55 filter with water from the cycled aquarium. That should help! ^^
It really varies, I wouldn't go for 4-6 weeks. It might only take you 2 weeks. Just test regularly and your tank will let you know! Good luck!