Def. aerate, pure 02 is even better. I don't rack onto cakes (except to attemp to fix a stuck ferment, which has only happened once).
What I like to do, depending on the OG of the new beer, is scoop out a measured amount of slurry (using mr.malty.com) and then pitch THAT directly into the new wort in a clean and sanitized fermentor. If the new beer has a massive OG, then its possible you may need the whole cake anyway, which would negate scooping any slurry out. I use a sanitized mason jar to scoop out the slurry and measure because the mason jar has ml marks. Super easy and allows you to pitch the proper amount of cells.