I sell the Kreem kit here, but I really dont like the stuff. It tends to peel off over time and clog petcock/filters. When I need to get my rusty tank cleaned, I used www.rusteco.com . Its a bit expensive but its guaranteed and there are no crazy films in the tank.

my .02
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MC21 300R w/SE bits, Rossi 2001
MC28SE Silhouette Repsol