Frozen vasoline supp: I'm diapered 24/7 and this works wonders to prevent rash.
I buy those cheap kiddie ice-pops...the ones made from colored water that come in frosted plastic tube ~ 1inch round x 12inch long - and snip off the top / dump out the contents.
Then I fill with melted vasoline (use hot water, a hair dryer or my favorite is a butane crĆØme broulee torch to melt the vasoline) and freeze at least overnight.
Then I use a razor to slit-open and peel away the plastic...leaving a 12" insertable plug that melts over the course of the day.
Unlike glycerine or mineral oil there is NO URGENCY with vasoline enema...Even with 120ml!!!
For that simply melt and pour into 60cc syringe. Let it cool a little and then fire whole syringe-full (or two) into rectum.
FOR THE MOST FULL FEELING WITHOUT URGENCY TRY BLUE ULTRASOUND GEL!!!
No Kidding -- watersoluible, safe nontoxic, inexpensive...I can typically get 200-300 ml in without trouble.
Note - Full rectum causes urgency ONLY with solids (stool) or irritants/stimulants (glycerine, saline, etc)