There’s this scummy film that forms on top of wort during biol. Should you stir that in or is it best to leave it alone.
also was thinking about trying whirlpooling using the CFWC to recirculate the wort. has anyone done this?
Sometimes I’ll fish it out with a strainer right at the beginning of the boil just for something to do, but I don’t think it matters. Generally it just dries to the sides of the kettle. Once you add hops, I’ll maybe stir it a little since it tends to capture some hop material.
There are skimmers and non-skimmers. It’s a personal choice. It will not hurt your beer to leave it in. That being said…I skim the scum because it’s easy, I don’t like the looks of it and I don’t want it in my beer. 
You’re either a scum skimmer or scum scorner.
As for using a CFC for whirlpooling, I suppose as long as you use a hop sock or spider, and situate your pickup tube up off the bottom of the kettle, you could recirc without clogging. Seems like more people shoot for one-pass cooling with a CFC though.
I was ok with the “white stuff” until it got labeled the scum…I may have just converted to a skimmer.
I whirlpool through my CFC. I use only pellet hops, so there’s no risk of clogging the pump, and after just a few seconds of whirlpooling a cone starts to form anyway. My pickup just sits at the edge of the kettle, pulling right from the bottom.
I like leaving the cold break behind in the kettle with the rest of the trub.
No stir. Boil chill and drain. Boil too hard and the hops will paste themselves to the side of the kettle.
I definitely scrape the hops off the side back into the beer - makes cleaning easier and it seems like a waste!
I skim if I have time during the brewday, but much of the time the hop charge contributes significantly more “gunk” than break material.
FWIW - most commercial breweries don’t bother, but they are set up to separate the break/hop material better than most homebrewers.