i would make two addendums to that:
1. You can go all the way to using neat diesel instead of oil, and i've done it before with no ill effects, but 50/50 Derv/Oil is probably fine for a starting point. Ideally you want to warm the engine up to operating temperature before draining half the oil out and refilling with derv, its not as effective on a cold engine.
2. If your engine is ropey, i wouldnt let it idle on the derv/oil mix. The thinner the oil is, the lower your oil pressure will be, and on our engine with its dodgy oil pump the pressure will often drop below 1 bar at idle on a hot day with normal engine oil. With some thin oil because its been thinned down with derv, it might get dangerously low. I would suggest using 1500rpm as a minimum, with short 30sec increases to 2k every few minutes, as that way your likely to ensure the pressure stays above 1bar.
Also, dont allow the turbo to spool up at all during the flush. I found using a small thin piece of plastic jammed in the throttle linkage moved the butterfly enough to hold a reasonably fast idle.
