Audible Shiny Gloss on Used Records--How to Remove?

No idea what that gloss is. Could be some record preserver like Las and someone has gone nuts with it. Or could be just the pressing itself.

If you want to give it another try in a washer…

I use knosti disco antistat record washer with TERGIKLEEN™ Record Cleaning Solution. I don’t see a reason why it wouldn’t work in ultrasonic. It’s removed old caked on dirt from record I bought on garage sale. No harm and they sound great.

You can buy Tergikleen on ebay. It’s a concentrate. Only need few drops. Read up on it. Give it a shot. 
 

Treatments like GruvGlide should be able to be washed off.

Some people use to wipe the record with lighter fluid (to clean the surfaces) that causes a sheen that is permanent. 

Try some Dawn in the sink. It’s a pretty effective general solvent.