Tripod/Monopod/beanbag: Just anything that offers you stability really
Take your time to learn to focus manually, it takes time but what I use even with my automatic lenses is the "sea saw" method. You go over the focus then back under then back over ever small adjustments Then one day you just "feel" the lens and have to do allot less adjustments.
For the rest shooting landscape the huge DOF the small aperture gives you doesn't gives you allot to worry about
For shooting buildings mmm yeah.. well after a while you begin to learn to do the "sniper" effect. After a while you simply feel the lens feel the body are one with the moment and are able to get it just right. It takes time.
I have an AF lens that I mostly has on Manual, I shoot my pictures mostly manual with it. In the begin that made it slower yes but now I am quick. I have the focus where I desire.
If you do landscapes you need something like a beanbag or a mono/tripod anyway. Longer Exposure times due to smaller aperture.
Manual Focusing becomes something you have to get feeling with. Photography truly can become an art on itself. As in watching a good photographer do his/her thing.. they just know what to do the only way to do that.. is doing it yourself.
Most fun part about the manual focusing ;) Is the freeze.. the way you learn to freeze your movements and go for it like a sniper.
You learn it it will go wrong a few times but you'll learn it. And using smaller Apertures obviously makes it easier to