Welcome to the SeeMeCNC Community

The best way to do multi-extrusion, assuming you're using a Cyclops or Diamond (as most Rostock users are), is to use the Wall/Short Wall feature to purge the old filament before starting with the new. Unfortunately, KISSlicer deliberately over-extrudes the wall. There is no way to stop it from doing this without causing it to under-extrude ALL support material, which is unacceptable. It draws the wall, pauses to retract, drools a bunch of filament into a blob, and then drags that blob over to the part. This leaves ugly pockmarks on the finished object.

The filament has been carefully measured and had the flow tweak adjusted, so it's as close to perfect as I can get it. It's also running at the lowest temperature it can tolerate, which should help control drooling. Unfortunately, the huge blobs deposited on the wall aren't something I know how to fix.

Since KISSlicer's dev has gone AWOL again, and might not come back this year or ever, I was wondering if anyone knew a trick to work around this. I hate to say it, but I'm looking at MatterControl's labyrinth of configuration settings to see whether it would be worthwhile to use instead of KISSlicer. I NEED good parts, and this slicer just can't do it the way it's set up now.