Hardly sounds like traditional way to do tan a bunny around here.
I've not fully tanned a bunny yet. I've cleaned and dried one (had it about 9 months and it don't smell), and it is like parchment, just thinner. Bunny skins when cleaned are very very thin. My first piece of skinning and hideworking however was a roe deer head (part of a lithics project so my uni department supplied the head but I had to give it back since I had removed the skin and ears). During that first project I was adviced that a stick works well enough to clean a bunny skin. And it does, if split and you have a knife handy to cut bits of flesh and member off when it gets awkward.
As for tanning, I've heard that liver works well, although usually with brain. Eggs would be interesting to try. Let us know how the hat goes. I'm working on the lining for a pair of mittens this weekend. I'm planning a fleecy outter and a bunny skin liner for extra warmth and to improve waterproofness. My problem is that I currently only have one bunny skin waiting to be used. So I'm going to have to send my partner out to get another. Then I'm going to have two skins to clean in the cold!