Focusing a manual lens on your 5DM2.

I recently purchased a Samyang 14f2.8 manual focus lens. I wanted to see if the reports concerning very good IQ were right. They are if you can focus it properly. My problem is my eyes. I wear bifocals and am having difficulty getting exact forcus through the viewfinder and I simply cannot see the liveview screen in sunny conditions. Have just come back from taking photos and most are out of focus because of the glare. How do other bespectacled photographers get around this problem or is there a very simple answer that I just haven't thought about?