I ended using two pair of needle nose pliers to get the thing in there a bit, then while holding it with one pair (so it didn't spring out to lost forever in the garage) would use a flat screwdriver to push it the rest of the way into the groove.
Also, make sure the case is covered so the circlip doesn't drop down into the case.
The above wasn't the most optimum and if I had to do over, I'd buy/rent the damn tool. I absolutely hated messing with those things.
I can't decide whether you're a sadist or a masochist. I went crazy trying to put in the circlip in the clutch ramp in the tranny side cover. I broke down and spent $10 for the tool. It was money well spent.