The way I handled it was to pour the prep liquid into a beer mug and pretended I was a chugging down a couple glasses of beer. It worked. Yes, IIRC the stuff was gross, but something about changing the psychological aspect helped me down it. I've had these procedures done twice and it's really no big deal now.
Having had a life-threatening health condition at the tender age of 38 (I survived obviously) during which one shocking procedure after another was carried out on me, nothing phases me now. In fact, this year I had the male equivalent of a pap smear done, where they stick a long cotton swab in your behind. The PA said "now you're going to feel X." I told him to just go ahead and do whatever he needed to do as I'd had every indignity known to god and man done to me and nothing phased me now. He laughed, but it's the truth.
