On our Zodiac we used the West Marine stencils, but instead of their included paint we used a back Sharpie permanent felt marker (one with a thick 1/4" tip). It worked wonderfully and was very easy to use with no mess or mistakes. The ink remained bold for an entire year and then some. Usually at the start of each summer season I would get out the Sharpie and freshen the numbers just to make them bright and bold again. This took about 10 minutes, but wasn't really necessary to do each season. I just liked them to look fresh. No stencil was needed to do this, just went back over what had been done before. Doing the numbers in this manner was very easy and looked great. The benefits to us were the ID was always clear and readable, numbers could never individually fall off, and were able to take off the number boards we had previously used which always seemed to get in the way or splash around when underway.
Rob