I have very limited experience with Manuel brakes. I have however worked on several Jose and Miguel brake systems so I'll give it my best shot..

(just kidding, couldn't resist )

Seriously, i would focus on two areas. Is the master an actual manual drum cylinder? Both fluid compartments(front and rear) are equal and small. I have seen some that have disc brake masters installed with all drums. It will work, but you will have pedal feel issues. The other area I would look is are the shoes glazed? This will cause the drum brake shoes to lose some of their ability to "self energize" when they come into contact with the drum wear surface.

Good Luck,

MB