slush does not equal crud, though for many people slush is pretty darn cruddy. As stated already, "crud" is when powder got partially skied out, has sat there a while and thickened. Or it could have been rained on before it was skied out. or perhaps not even skied out at all, but just sat a day or two. Or if you live in the Pacific NW it is pretty much crud the minute the snowflake hits the ground.
Crud is WAY worse than slush. If you know how to ski slush its an absolute JOY to ski in. In my opinion there is nothing that makes crud that joyful except for fatter skis. Go fat enough and then PNW crud does start to feel more like the pow we want it to be.
Contrary to current popular belief, you do not need fat skis to love the hell out of slush. It might be that fat skis would deflect too much in random directions while your skinnier skis would sorta submarine through with just enough planing.
You do NOT need to ride across the top like you do in powder. But you do need to go fast and you need to make huge edge angles that bury your skis into the slush and use the whole base of your ski to arc a turn. Do not try to make skids or pivot based turns (no no). Go for the purest arcs you can fathom. Don't worry about speed, the slush will slow you down a bit too and anyway if you fall...its eh.....only slush. Try to make the deepest trenches and biggest rooster tail you can by cranking it over. You cannot over-edge in slush. You don't even really have to worry about boot out. In fact there is so much sloppy technique you can get away with in slush its amazing..you can just wail down the hill with too much banking and all kinds of atrocities, making huge rooster tails and everyone will just think you're some kind of slush god.
Oh, pick slightly steeper runs and make sure you have wax.
if after all that you find that the snow is making you slow down so much your nose almost touches your ski tips from the brakes being applied, then you must either find a different run or call it a day. another thing about warm days like that is that picking the right run to ski on is absolutely critical. There can literally be an hour or two window for each run where its optimal and the rest of the time it can be anywhere from sub-par to downright terrible. You have to follow the sun or shade, depending on how you want to think about it. With experience you'll figure out which runs to pick and how to know whether a run has melted to just the right level of slushiness to be good to ski on or whether its currently in a state of semi-frost that is sure to give you a broken nose.
Have fun, good slush is a lot less common to find than even a good powder day.