I know you asked for Brooklyn but just want to add in that Michaels offers wilton decorating courses for EXTREMELY good prices. I took courses there. They charge $20 total for each level. The level is four classes of 2 hours each. Total 8 hours. Supplies not included but michaels always have great coupons.
There is a Michaels on the Upper West Side close to several trains and buses. There is also a Michaels in Queens but not easily accessible by public transportation.
