As can be seen from all the replies, many use their "pet" concoctions and products. Me....I like to keep things simple and fully understand that BP fouling is completely soluble in "plain water". Whether one prefers cold, tepid or hot water is really
immaterial....plain water will do the job.
I use 120 degree hot water {that's what my hot water heater is set at}, but due to impurities in untreated water, cold or tepid water probably should be used....my water after going through an iron filter and softener is the next best thing to distilled water.
A hot bbl dries quickly and completely and when the Oxyoke !000 Plus lube is generously applied into a hot bbl, it gets into every nook and crannie and when cool, coats the bore w/ a waxy layer that prevents air contact. The Oxyoke "stays put".....in other words it doesn't migrate to the lowest areas and leave the higher areas susceptible to air contact.
Through the years, have done the above cleaning and used Oxyoke lube and don't "go over again" for long term storage.....the bores of my MLers have always been rust free.
As a point of contention....don't think the addition of soap to water really helps dissolve BP fouling...water alone will do the job, but the "modern mindset" somehow seeks more complication. Soap is a wonderful cleaning agent that was invented a long time ago, but is quite unnecessary when cleaning the bores of MLers.
But, "whatever" is used to purge water soluable BP residue from the bore, if it satisfies the "modern mindset" and does "get the job done", that's what should be used.....Fred