Nik, easy way to start is to bottle the cake. you can get a series of small water bottles, and mix the trub up in the fermenter with the yeast to create a slurry and fill the sanitized bottles straight from the tap. Not awesome practice as the cell counts will vary between bottles but will work fine if no infection is harvested / created.
Just put them in the fridge and when needed lump them into the next batch.
Pitching onto a cake is a massive overpitch, whilst it will work, this process is basically the same but will be less of a massive overpitch.
I will dig up a thread on here by another Nick about bottling and reusing the trub. It is quite a rustic process but very simple. I do it on occasion to reuse expensive yeast.
Edit: here
http://aussiehomebrewer.com/topic/45716-bottling-fermenter-trub/
Cheers,
D80