I like to have a bigger aperture on my carrier. Just enough to see the rebate, I then use the easel to either remove the rebate all together or to leave a thin black line. I don't like that carriers often crop 1mm from the neg and I've always had Newton's Rings issues with universal carriers.

I use a Swiss file, go slow, keep checking against a negative to see your progress. Put the carrier in a vice rather than holding it in your hand.