Over the decades have tried many things.. methods detergents mixtures of the above.
 From dishwash powder , liquid, soap powders, milking machine cleaners,  highly concentrated version of car wash station detergents.
Mixed with soaking, water blaster , scrubbing, types brushes.
 Oh list goes on

My objective is not so how hard, as its not hard work, but how easy quick from start to finish, equipment away and having a coffee.. I note even things like the petrol water blaster is pretty much permanently setup the pull the cord and go... its about time.

And what is working the best after 6 or 7 hrs of smoking is the following.
1/ Start with clean dry racks..canola oil in a aersol , good coverage but not excessive amount... lay food on and smoke.
2/ As you remove food from racks, do it hot as lifts the food off without any sticking... and leaving stuff on the racks.
3/ Throw the rack in a 50L fish bin full of RAIN WATER. Rainwater has a pH of about 5.8.. tap water more around the 7 ... and leave for 3 to 'when get around to it' days.
4/ Good blast at an angle both sides with a strong but fine flat hose attachment.
5/ Then take each shelf, a quick , and that is all it is very quick scrub, more a wipe with a old fashioned shoe polish brush ....another quick rinse, drip dry.
6/ A mist spray with canola oil again,, stops any rust where chrome has peeled off type places

Then when ready for next smoke.. start at 1/ again

Its a bit annoying that one trys so many methods , mixtures for so many yrs and end up going back to what my Dad did in the 50s/60s...a 'bucket' of rain water.

Im sure others have banged their heads around this 

Oh the smokers , both steel cabinet types, every so often I foam up with GT18 or GT20 detergent, then blast with the water blaster.. let dry and a good , only a bit more than a mist coating of canola oil.