Some of observations on my colon tube experience.
Open end tubes tend to snag and kink more often than closed end tubes. Closed end tubes seem more durable.
My 'best size' has increased every few years. Twenty years ago I was using fr28. Now it's fr38 or fr40. I'm figuring on fr42's when I find a good source.
Lubing the 'lead' 6" with Crisco helps. A good 'rub down' of the rest of the tube with a softened bar of Ivory seems as helpful as any other lube. However, if I were overly sensitive to soap I'd probably opt for something else.
First enema is heavy on soap. Insert about 6inches of tube, then flow in some soap.
For the follow-on enemas I renew the Crisco and lube the rest of the tube with something like Astroglide Natural or Slippery Stuff gel
Maneuver the tube into the Sigmoid by changing posture and twisting the tube. (helps to have plenty of hose between the tube and the bag -- a Higginson or other inline pump may be helpful in keeping track of how much solution is inside. )
Inject soap solution as I go (trying to have several ounces ahead of the tube until reaching my intended injecution point.)
Whenever there's a hint of an obstruction, it's good to back out a few inches, inject more soap and try again. (otherwise I'll trigger a spasm which will brings down the curtain on the whole session.)
Every colonoscopy, I ask the doc about any major diverticla (pockets) and their location. I keep those in mind stop early to avoid getting hung up in a pocket. For example. I know I've got a major pocket at 53 centimeters. I have a piece of black electrical tape around the colon tube, 20 inches from the tip. When I'm inserting, I stop when the black tape touches my anus.
ENJOY !