Tying the Brassie

Hi -

I am a beginner fly tyer with about 6 months experience. I have a
question about the size of copper wire I should be using when
attempting to tie a Brassie. I have three spools (UTC) two of which
are marked *SM* and the other is marked *BR* - the latter appears a
tad larger. Is there a particular size I should be using? The
illustration in the manual is rather large, and the wire looks thicker
than what I am using. I am using a Mustad Caddis Curved 1X Short Size
10. The recipe calls for a 12 - 20 hook. Just don't have any on hand
right now.

Appreciate any advice from those more knowledgeable than I.

Thanks,

Dick Williams