Brightest / easiest to focus manual SLR?

Yes. Winner by several lengths is the Leica R-8 / R-9. Bright AND Contrasty, which are usually conflicting qualities.

After that, a toss-up between an EOS 1v (with suitable screen) or a Nikon F-4.

Followed at a great distance by the rest of the field. Lots of good-to-focus cameras there, but the 3 really are superb.