I'd scrape off the foamy things with a razor blade as much as you can, and put some boiling water on the remnant hard glue to soften it (even immerse in boiling water for a few minutes). Then apply some Goo Gone/eucalyptus oil onto the glue for several hours. Roll off with fingers, or a non-scratching kitchen scouring pad, impregnated with soap, if really stubborn. Then scrub all over with soap and water in the sink.

It'll likely never all come off, but good luck

JB