[X] Send enough people to evacuate all people in any population centers as well as warn the Kislevites about a potential daemon invasion, if needed give them a insignia of Mathilde Weber or any symbol that links King Belegar or anything that symbolizes Karak 8 peaks involvment.
[x] Fortify the Karak entrance with the steam-wagons, use the fortifications as distraction or camouflage for the plan of emptying any nearby population centers, try talking and arguing loudly about abandoning the population centers, make it look convincing such as sacrificing the few for the many. Have a few fights break up to sell the deception. Be sure to remove as much food from wagons, in case a hasty retreat is needed.
[x] If possible, fortify a random area as a decoy Waystone, that may further divide the daemons.
[x] Consult dwarves on possible secret entrances, and do best to fortify against flanking of the entrance to prevent ambushes. Talk to the other wizards to see if anyone can specialize in locating secret entrances in mountain.
This plan gives allowances to help any surviving dwarves in the Karak, it also assumes that one day of travel won't weaken the Slaaneshi horde much, and may in fact give them time to group up on the road,