How to pre clean a very dirty LP before Ultrasound Machine?

Will do sleepwalker, looked it up your correct. For me if album has mold spots I through them away. If just dirty and mold smell, steam, machine then ultrasonic.

Get a new, fine-bristle paint brush and some organic dishwasher soap. Suds it up in a bowl with a bit of tap water and run the brush a couple of sweeps around each side. Rinse (yes, even under the tap, carefully, or with distilled if you must), let dry then put the shiny clean LP (for it will appear so) into the Ultrasonic for the final touch. Fast and effective. 

I put them in the dishwasher - no joke.

Get some Audio Intelligent #15 mix 50/50 with warm water and set the record on a glass. Lavish the surface and let it set on the record from 4-5 minutes. Circular brush lightly with the white brushes from Last.The little white brushes are cheap and durable but can be disposed of without high cost. They are soft so not likely to grind anything in.  Rinse with warm, almost hot water and repeat other side.
Mix up some Audio Intelligent Down with dirty and repeat, again washing with warm/hot tap water. Down with Dirty mixes up about 5 gallons of cleaner so it's cost effective. Don't worry, the tap water will not deposit because you're going to immediately head to your V8 and use the distilled water of your choice for the cycle. 85 degree water is approved by the Library of Congress.  
I use a homemade ultrasonic bath, again 85 degree clean distilled water for the final step. No cleaner goes in my ultrasonic. I don't want it on the record surface when all is said and done. I have used reagent water from Amazon, Nerl 5 gallons for around $100 delivered. Couldn't tell a bit of difference in that from good distilled water from Walgreens or Whole Foods. Maybe you can. 
Anyone who knows anything about the efficacy of surfactants can tell you the temperature of the water ups the activity of the substances attacking the mold dramatically. My ultrasonic has a heater, hope the V8 does as well. If it doesn't just buy a heating wand and get the water good and warm. 
I air dry because I don't want anything touching the clean surface and towels promote static electricity. Just get some dowels of the right size from Lowe's and spindle the records. They dry in about 15 minutes. I notice the water in the ultrasonic gets dirty a bit quicker when the water is warm, if that tells you anything. A bit too quick to be spending $100 per refill.
My record collection got flooded in 1982 and while cleaned at the time, some mold developed on quite a few. This worked for me.
Good luck and happy listening.

Thanks so much for all the great advice!