ORIGINAL: buzzard bait
The one idea here that sounds sure fire is the diesel fuel. Does it ignite and run well enough in a glow engine to clean it out? I'm wondering what happens when you put something with 25% ether inside a four stroke and fire it up. Maybe it's fine. If so, it sounds like a great technique. If not, then keep a bit of no nitro all castor fuel on hand for a few second run at the end of the day sounds like the next best thing.
Jim
The exhaust residues of diesels are bad too. A diesel engine should typically be left with the piston in BDC so that the bad fumes can get out of the cylinder in order to avoid rust. MVVS also recommends that the muffler is removed after each flight for the same reasons.
To avoid gumming up, due to the full castor diesel fuel, a bit of after run oil is also useful.