cleaning the top of primary fermentor

So I've read that I should clean the top of the fermentor (I'm using 1 gallon glass jugs) after the krausen falls and before I top up. What do I do that with? A bottle brush? Wouldn't that make all that crusty gunk fall into my cider anyway?
Is racking an option now, or is this too early to rack? (It's been about a week since I pitched yeast, and the krausen on some of my batches has reduced to a thin layer of bubbles)

I've never read to clean the inside of the carboy while cider or wine is in it. That sounds just crazy! You'd risk infection by inserting a bottle brush or something, and then you'd have all that awful nasty stuff that's in the krausen ring in your cider. I would never do that!

When the sg is down to 1.010 or so, you can rack. Or you can leave it where it is for a while. I'd probably rack it to a clean carboy and top up.

thanks for the quick reply!

ok, maybe what they meant was to clean the outside if any spilled over i guess..
so anyway is it ok to leave a 4 or 5 inch headspace for a while? i guess that's all CO2 now anyway, right? or is it better to top up sooner? Do I even have to worry about that gunk on the sides? Maybe it won't hurt anything if the cider soaks in it after I top up? or wait till I rack to top up?

Don't top up in your primary. The only point in toping it up is to get rid of the air/oxygen in the fermenter. If it's a primary fermenter and you haven't been opening it 3 times a day, it will be nothing but C02 in it at this point. You don't want the gungk on the sides to get back into your cider. So don't top up until it's in the secondary, and then only do it if you want it to be overly dry. Most of the time, racking it to the secondary will shake loose enough C02 that you won't need to top it there either.