Dominator Jacques has good tutorials to reference but they are very long. I messed around with detuning a lot last year because I had some Völkls that 1) I didn’t prep correctly 2) they were edge high.
I got rid of those and successively detuned some Lines after.
You'll want a file (I used a Toko World Cup file M), gummy stone (possibly fine sand paper) and a Diamond file. Here’s a good link
I would suggest following these instructions but use a true ski file and hit it with the gummy stone after and then a Diamond file to really smooth it out. What helps too, if you can wait, is ski around and avoid rails for the first day or two so that the mountain will naturally detune the edges a bit more.
Thats just my 2 cents.