I understand what you're trying to do, but the Bobber with a Brain is meant for bottom fishing. (And it's not even very good at that.) A better option is a simple bubble float like this:
Are you saying you tied the fly line to the bobber? All you need is mono.
Having said that, I'd still recommend getting an inexpensive fly outfit instead. No matter how hard it looks, if you can walk and chew bubble gum at the same time, you can learn the basics in less than an hour. Fly casting is fun, and playing a fish on a fly rod is fun. It's well worth learning.