Do they use the 1/4" or the 3/8" threads on the typical black
fibreglass chimney rods at home depot? I want to order a brush. I
think its quite large so I'd go for the 3/8 but I don't reallt
remember (I'm at work now so I can't check).

I presume I need an 11x11" brush for a chimney that size? No need to
go any larger is there?

Thanks!

Dean