I sharpen mine on a Tormek, their jig works well for this application. However, it might be a bit pricey just for one application.
I reground my skews to a curve a long time ago. I have wondered once in a while if there really was an advantage. A while ago I had an opportunity to teach a class emphasising the use of the skew. The class was provided straight skews. I found that I like the curved one much better. One example: in turning a spinning top, with the point towards the tail-stock, the straight skew does not provide an angle to smooth the handle as one gets to the finished shape, one has to, almost, use the whole edge; however, with a curved edge one can easily used but a small part of the curve. In my opinion the curve opens up a lot of possibilities for versatility.
By the way, it is very possible to, in this example, to start a cut to smooth the handle of the top with the long point and continue the cut all the way to the short point. The key is to always support the part of the tool with which one is cutting.
I've developed three rules for making a cut with the skew, beyond the basic: tool rest, bevel, lift handle to cut. First think through the specific cut, even stopping the lathe, locking the spindle lock and 'walking' yourself through the cut to make sure you have all the right handle movements. Sometimes as mentioned in this thread and the other active skew thread, they can be complicated. Second, use a slow lathe speed when making the cut. There are several reasons for this. Catches are usually less exciting at slow speeds. The cut can be watched and thought about as it is being made. And a third rule is, somewhat related to the second, don't overfeed your tool into the wood. This is like trying to push a pieces of wood too fast past a router bit, through a saw, a jointer, etc. I think we think just because we have the rpm's cranked up we can move through the cut with lightening speed. A sharp tool should smoothly advance through the cut without a lot of pushing. Make the cut slowly and smoothly. Oh, and lots of practice is encouraged.
I suspect the comment on the lower 25% is in reference to, closest to, the point that one is using. That is a good, but maybe conservative, rule to use a starting guide. in my opinion.
Al
