I tried the ultrasonic on the latex goo I wasn't able to scrape out of the stainless sac housing, and it seemed to work. A chopstick slid to the end and out revealed no more black stuff.
PVC sacs ordered from David.
I forgot to answer that question. Naphtha. Naphtha will break down the goo, and a long medical swab with a wood stick will reach inside to clean it all out.