Cleaning Kodachrome slides?

I have some 1940's vintage Kodachrome color slides that I want to
clean, re-mount in Gepe mounts, and scan. Any recommendations
on how to clean them safely? I tested one today in some warm
water and Kodak Fotoflow. The emulsion appeared to bubble up,
which made me nervous. It settled down again after drying, but the
light areas (sky) look a bit "crazed." It may have already looked
that way, I need to take a close look at some of the others.

Thanks
-Mark