I think the original plan of the microbes will be sufficient to do what I need to do to clean out the tank. Its just a residue coating which as some have pointed out may not pose much of a problem even if it wasn't removed. After the microbes have been allowed to do their thing for a period of time I will start using the tank for bulk storage, slowly pumping from it to a pair of 330 gallon tote through a bank of carbon filters which will remove residual VOCs. Then pump from the totes into the saddle tank. Add the water treatment to the totes.

Thanks everyone for the advice.

So I'm admittedly a bit late to the party, but we have used the microbe stuff before in my line of work (heating oil is frankly so ingrained in my family I'm surprised I don't bleed the stuff). It works exceedingly well. We took the oil and stains off of a cement floor with the stuff. Now getting the stuff around the tank might be interesting, considering you can't get into the tank to apply the stuff by hand... My thought? Say you take something like a rotating lawn sprinkler, You could take two or three, mount them together to cover all angles and use that sort of mcguver solution to apply the cleaner. The problem will be getting it out. You may need to drill some sort of hole for it to drain from, or have some sort of diptube in there to pump it back out... I have an idea in my head, but frankly would have to draw it out.

I am just going to fill the tank with water, add the microbes and occasionally throw a couple hoses in to circulate the water around. After a couple of months of that, and once I do not see a sheen of oil on the surface, I will just start using the water out of the tank. The carbon filters will take care of the rest including the microbes and their waste products.