Hey, as long as it works and gets the job done. Besides doing it yourself is cheaper, and you know that it is done right.
Me., I open and drain the 4 petcocks, which from what I have read leaves me about 4 gallon left in the engine. So then I put 4 gallons of 100F blue antifreeze in a 55gal drum that is cut in half length wise with a Rule circulating pump and a pair of muffs. I light her up to about 1100 RPMS. I run a 160 degree thermostat. I will run her till it reads 170, then I shut her down. Total cost antifreeze $50, I've had the pump and drum for as long as I have had my girl. (1992)
If you have a system that works for you, (other then paying for it) please let us know, it may help someone else to do theirs.
By the way, does anyone know what the marinas get to do it?