Alkaline bath softens the remjet backing. You don't want it to mess your developer so use a separate prebath with some carbonate or bicarbonate (soda or baking soda) for a minute or less, without much agitation, and then, under water, scrub the remjet backing off. I have done this by running the films through my fingers 2-3 times, every time in new clean water. It's a bit messy and this way you risk having some remjet deposits on the emulsion side, but works usually quite well. If any remjet remains, it will soften completely in developer and you can scrub it off after fixer, in the final wash lights on.