I've read recipes that mention spraying a pan with regular cooking spray (Pam, for example), spreading the oil around with a paper towel or pastry brush, then spraying again and dusting with flour.
If it's for someone else to share and you need to think at least a little about presentation, I'd say line the pan with foil, spray that, flour it, and then just remove the brownies, foil and all when they are done. I've seen similar ideas when the baked goods in question are sort of delicate, and the foil lets you pick the entire thing up out of the pan, instead of taking the risk of turning the pan over to get them out.
I'm reluctant to cut things in the pan, since I don't want to scratch my pans.
A fruit is a vegetable with looks and money.
Plus, if you let fruit rot, it turns into wine,
something Brussels sprouts never do.
P. J. O'Rourke, humorist