I use spotone also, with a very fine (and expensive) brush. One thing I do not mentioned above-
I spotone large groups of prints all at once. I start with straight toner (one or two drops in a Schnaps glass (funnels to a small bottom) and go through the whole stack of prints, spotting only the darkest areas. Then I add some water with an eyedropper, go through the stack again, hitting lighter areas. I repeat this getting lighter and lighter, eventually a full schnaps glass with almost no actual spotone in it, mostly water, by the time I get to the highlights. This prevents the dark outline, which I believe results from the toner being darker than the surrounding area. I also keep a wad of tissue handy to blot the brush if the area is very small. It may seem like overkill to some, but over time, I've had very few "spots" where you can see the toner.