If I am in the woods and my knife blade need to be touched up (normally if they do not shave arm hair), I use the diamond file on my Leatherman wave. I have found that it puts a nice edge on Buck's 420HC pretty fast. It works well on 154CM and D2, but I do not know about other steels and the LM file.
To get your knife razor sharp, you may need to reprofile the blade. That means thin the shoulder. If you have used this knife and sharpened it many times, it is possible that you have removed enough metal that the factory bevel is no longer there. I have found that Buck knives can take a pretty thin edge (around 12-13 degrees per side) and it slices like a razor.
As for the pocket sharpener, I have never had much luck with them getting an edge like I like. You might want to keep an eye out for some stones at yard sales. You can buy a few more diamond pads which would work very well at getting the edge you want. You will need different grades such as fine, med., ect.