Mount ski in the vice with the side edge vertical & the base facing away from you. Secure the tip & the tail in the lateral vices. Put masking tape down the sidewall of the skis to keep the filingd & stone dust out of the bindings. 

Stone down any side edge damage with the alu-oxide stone or coarse diamond stone as the impacts with rocks etc case hardens the edge so that a file can’t touch it. The alu-oxide stone is best used with a side edge angle guide but with a bit of practise can be used freehand.

Using a side edge angle guide, file (if required), stone & polish the side angle as per the base angle. After initial angle setting & polishing etc, then the edges can be kept in tune by regular (daily in icey conditions) use of medium & fine diamond stones.

Wipe the edges with fiberlene & give the edges a wipe over with Zardoz Notwax to prevent rusting.

-it's a real pain to apply smoothly.

-it either peels off when it shouldn't or is so sticky it leaves a residue on the base.

-when filing any swarf is released over the top sheet side of the ski away from the base so just mask out the bindings & use a paint brush to clear off the bits.

-I'm concerned about the thickness of the tape altering the angle of the side angle guide, especially if it’s creased.

-it's expensive!