yea those engine drain plugs are cumbersome; I just do more frequent follow up flushes (first with regular water, then with a few gallons of distilled water)
these are a pain to burp; just make sure to loosen the air bleed bolt & make sure to have the front end lifted up...
i've seen other people use those coolant funnels with greater success than whats in the pdf service manual...
hmm, with this tool, i don't see many people propping up the front ends (in youtubes)... pretty neat!