Recently did some slicking up on mine, it's easy. Both of my MK II's had pretty good actions to start with, but I decided to take it up a notch. It's actually very simple. After you remove the bolt from the rifle, carefully remove the spring clip that holds the firing pin, extractor, and cartridge guide in place. You can lift one side of that spring up with a small flat tip screwdriver, then keeping a hand on it you can lift it off. Slide the extractor, firing pin, and cartridge guide out and clean everything up.
Since those items are stamped, the edges can be a little rough. Some fine sandpaper (I used 600 grit) can be used to clean up the rough edges, then lay those on a good sharpening stone and work the flat sides to remove any burrs. Once those are done, dress the slots they fit in on the bolt. I used a small fine flat file that fit those slots and worked it to remove any burrs or tight spots in those slots. The other three parts should move easily in the slots.
Before you put everything back together, take a Dremel with a felt wheel, add some Flitz or Mother's Mag polish, and lightly polish the bolt (not the blued portion). It doesn't need to look like chrome, just shiny and smooth. Once everything is cleaned up, reassemble everything adding a light coat of your favorite oil. One thing I found that help keep my sanity in check was to install the firing pin then install the spring clip. Once it's in place, you simply slide the pointy end of the extractor and cartridge guide into their slots and under the spring, then push them into place. It's a lot easier than trying to hold all three in place and fight the spring.
My action went from pretty good to very nice doing this. Hope it helps.
