Recently started working at a company that the previous workers had no clue about chain sharpening. Never took down the depth gauge and seemed to have sharpened with 3/8 pico files for full 3/8 chains. Was told they just put new chains on once they quit cutting. Have about 30 25" loops to sharpen. Just ordered the Oregon 410/120 grinder cause it took me an hour to correct just one loop with a hand file. Never used a grinder so am seeking tips to correct all the damage done. Guessing i need to start a bit like a stump grinder and correct along the link then "get the gullet" then the hook of the tooth. Thats how i did it hand filing but again never used a grinder. Any tips or link to a good instructional video would be greatly appreciated.