First Step is good stuff, Jim
We've used a fair amount of it in the past.
Tim, most any "sledgehammer" type pre-spray will work.
Prochem Powerburst
Bridgeport Power Break
Bridgepoint Flex (though i don't think it's as "wicked hot" as it used to be)
Prochem
Ultrapac #711 will smoke 'em in extra strong max+ dilution rates
Chemspec Enzall
just to name a few.
the key is to spray down PLENTY and let dwell plenty long
(I doubt they'll pay for mechanical/rotary agitation)
also, most of those chems I mentioned need to be mixed in hot water.
and don't be afraid to go max+ dilution ratio, though there is a point where going to far over max+ dilution is just wasting chem for minimal gain
..L.T.A.