I use the Pipe Net reamers (4 in a set) and follow up with 150 grade fine sandpaper. (I tried the Senior Reamer but I find it unwieldy). You just have to go slow with an easy hand with the reamers, checking your progress. Reamers are best for pipes having heavy/ heavier or uneven cakes, e.g., unrestored estate pipes, and the work goes much faster than sandpaper. But if there isn’t much cake or unevenness, go straight to the sandpaper.
Thanks to my grandsons, I came up with my own set of SANDPAPER REAMERS. They were having a sword fight many years ago with my cheap pool cues and broke one of them. As I was about to throw it out, an idea struck. In short, I cut the pool cue into 5” lengths, then cut a lengthwise slit in each 5" section. The slit serves to hold the sandpaper’s edge, and then I wrap the remainder of the 3” x 3” square clockwise around the section and begin to add the final ream and smoothing. As a pool cue is tapered, there is always one size on hand that is ideal for most any pipe having a conical bowl or where the bowl has a smaller circumference towards the bottom than at the top of the bowl. For pipes having uniform circumference chambers, e.g. pots, you can use the appropriate size wooden dowels that are widely available.
I would never nor have I ever used a knife to ream a pipe. It is difficult to maintain a uniform cake reaming with a knife and a slip could cause irreparable damage.
A cigarette is to be smoked. A cigar is to be enjoyed. A pipe is to be savored.