cleaning fluid mix and match?

Certainly, there's no reason you couldn't mix and match. But you may want to experiment a bit first. I find the Walker Audio Prelude Step 2 cleaner superior to Disc Doctor Miracle Record Cleaner even without the enzyme step. But, there is no question that the 32 oz of Disc Doctor concentrate goes further once you make the recommended 2:1 dilution for the actual cleaning solution.

The ultra pure water rinse makes a big improvement with any of the cleaning fluids (DD, Walker, AI) over any of the distilled water I've been able to try from the grocery store or local drug store (e.g., CVS). I suspect switching to a Reagent Grade, Type 1 water would be equivalent to the AI or Walker ultra pure water, as discussed in another thread. (FWIW, I admit to economizing in the enzyme step by mixing the enzymes with a RO/filtered water rather than the ultra pure water, but I continue to use the ultra pure for all the rinse steps.)
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Check out the thread on steam cleaning and give it a try. You'll be very glad you did. Go to the nearest Walgreen's and spend $20 on a Perfection steamer. You'll find that you can jump off the cleaning solution merry-go-round and just use what you have. All you need is a good, pure water for rinsing. It should be very pure, not distilled. I like the AIVS solutions and rinse water. I bought a bottle of the rinse and I've cleaned probably 50 records and still have about 1/2 the bottle left. It really only takes a few drops spread around the surface to rinse. I also use the AIVS cleaner right after steaming. I've found I don't need more than a tablespoon of the cleaner when I use it after steaming. I haven't had to use any enzyme cleaner since I began steaming but I still keep some of the AIVS enzyme around.

Thanks for the reference to the thread on steam cleaning. I hadn't really taken it seriously before but after reading the thread sounds like something I should have tried a long time ago.