I try to replicate the angle of the factory edge, until I reprofile than for most medium sized folders, I try to make it somewhere between 20 & 22 deg.
I usually accomplish this freehand by laying the blade on the hone and tilting/lifting the spine up until the angle is matched, use a black sharpie to mark the edge till you get used to maintaining an angle. I also can't stress that you practice, practice, practice, when I say practice I'm not kidding. I figure since I was 12 I've probably sharpened 1,000+ knives,(ruined a few I'm sure
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This may help:
Having been sharpening my own blades for the last 30+ years I've come to notice a few things in regards to what you use to sharpen a knife. Diamond hones remove massive amounts of steel and sharpen a blade fast but even with the finest hone you will still need to finish your blade on a strop or ceramic hone to smooth out the edge. Always sharpen at the desired angle,(between 17-24 degrees, depending on the thickness of the blade) till you get a wire edge on one side, (the best way to feel for this is to slide your thumbnail from the spine side, or back of the blade towards the edge) when you encounter a wire edge it will feel like a little lip has formed where the wire edge has rolled over. Next sharpen the opposite side till you achieve the same result. Done on a Fine Diamond Hone, finish off by repeating the process using lighter pressure on each subsequent stroke and the wire edge will become smaller. When the wire edge is barely noticeable with your fingernail. Finish with a leather strop and stropping compound by applying a reasonable amount of force and dragging the blade backwards on the leather at a slightly less angle than you sharpened,(the leather will actually curl around the edge of the blade and wear off the wire edge) after a few strokes on the leather on both side you should have a finished edge. When the edge of the sharpened blade is rested on the smooth part of your thumbnail it will dig in, (bite into the nail with no additional pressure), Your knife should now be shaving sharp.
Diamonds are more aggressive and faster than wet stones or oilstones but will accomplish the same results with a smoother more polished edge, and depending on the grit of the stone may take a lot longer. The key either way is repetition, the more you perform the same task your brain starts memorizing the pathways through your body needed to accomplish this task. Eventually holding an angle, smoothness of stroke, all become second nature, and the task becomes easier. Thats why it always looks easier when someone else whose good at it does it.
My way is not the only way but it works for me, if you feel confident enough to attempt your own blades, start on a cheaper knife that your not afraid of ruining, and remember its easier to sharpen a knife thats not dull, than to sharpen one that is. So dont wait till your knife wont even cut butter before you dress up that edge. LOL
PS as for my preference I prefer a diamond hone just because I think it's quicker, and more versatile I can accomplish the same thing with one hone by just varying pressure to the blade as I sharpen.
