I just viewed the PS like any other 800 word assignment and had it out inside an afternoon.
Of course, I was under different time pressures, being that it was already December and I'd just decided to apply.
I was the same way. I tossed around a couple ideas in my head while at work, came home, turned on my computer, and wrote my PS in 15 minutes. I sent it out to some friends and made some minor grammar and wordiness changes, but for all intents in purposes my PS was done. Then again, it was also December for me so I didn't have the time to spare, either.
I wish I had some advice because I know how taxing the application process is, but I really don't. The PS just came easy to me.