I happen to prefer magnets because the magnet makes the visible parts of the hair push inwards. Any scheme that chops off polygons or overpaints them in post makes for hair that goes up straight until it meets the hat then is chopped off -- not very realistic. Of course, there will often be a few fly-aways. It is hard to tailor a magnet just perfect. I err on getting the hair to be visible in the places where it should be, and I'll touch up in post the places where it shouldn't be. And, yeah, modeling is even better. Nice thing about the magnet is that it will more-or-less work with any hair you put under the same hat, thus more flexibility. The only problem I have is remembering which library I stored the thing in!