I tend to wipe my bowls out after every smoke with a paper towel to keep the bowl clean. Cake still builds up, but I use the second blade on my Case knife, which fits the contours of the bowl great, to keep it trimmed thin. But, I don't suggest folks that don't have the finesse down of using a knife to get a reamer. I've never used a reamer, but I would think it takes less fine motor skills to operate one than a knife. I've seen some rims buggered up by someone who wasn't comfortable using one.
And, I really like the idea of sandpaper and a Sharpie. That's an excellent suggestion.