I've heard a lot regarding which ammo you WANT for the Mosin's, I fire Wolf and Brown Bear exclusively in mine to reduce barrel wear from corrosive ammo. But, that's just me. If you're looking for the bestest, tightest groups ever: reloading is your best bet. Because of how much these guns have gone through, their reaction to different ammo is different in many cases. So, just buy all the ammo you can and find a round you like or reload till you find a load that works.
That's my advice.
Also: to clean the barrels? Mine took about 15-20 patches originally to clean and about 8-10 after each time I shoot. Then I use a brush. My barrel's a pretty good looking one to begin with, though. Also, I've been fine with Hoppes #9.