I'm pretty good at navigating off trail with a map and compass already, can plot points and take and follow bearings with reasonable accuracy, and like many folks who have learned by doing am better than any of the aforementioned at visualizing map features and reading micro-terrain. Prompted by doing an adventure race this past weekend, I'd like to improve the exactitude of my orienteering. My partner and I used altimeter watches and the aforementioned skills to good effect, but a friend with a background doing transects for the USFS was able to follow bearings to some very difficult checkpoints with impressive accuracy. I'd like to get that good.
Any suggestions for online sources, books and courses that go beyond the basics would be appreciated.