I think it ranges. When I had mine last year at this time, I received a packet of info from my doctor that mentioned four or five different preps, and mine was very different from anything I'd heard before. I started two nights before the procedure with a double dose of Milk of Magnesia followed by a double dose of Dulcolax. Then on the day before the procedure, starting at noon (? I think?), same regimen every four hours, each time followed by at least 16 oz of water. I found it to be tolerable. I think the last dose was around 8pm the night before and then I had a regular dose of just one of them (I can't remember which) at 6am the morning of the procedure. I didn't get nauseated, which had been my fear, and I didn't have any cramping. The MoM taste is less than desirable, but overall, it wasn't too bad.
For the rawness, I used unscented baby wipes, and to be honest, Boudreaux's Butt Paste. For hydration, I purchased tons of options, and honestly drank mostly just water, with some tea and some sparkling water. I tried one serving of broth and didn't like it. I had coconut water, Gatorade powder to mix in, ginger ale on hand but never touched it. Mine was a diagnostic colonoscopy, too, (it was six months before I qualified for a screening.) I didn't have GI issues but I was super sick and didn't have much of an appetite to begin with, so water was pretty much all I wanted. I did struggle with the low residue diet as I don't typically eat like that, but again, little appetite meant not much of a struggle. I was eating a lot of eggs at the time, anyway, as that was one of the more tolerable foods then, and just had them on their own without the veggies I usually added. And toast. I don't know if this was allowed or not, but I had sourdough. I don't like white bread so I felt like it was better than having the multigrain I would've gotten. For clear liquids, just the water, tea, and seltzer.