I've only worked Osage once ans I found it much easier than Yew as the difference in texture between the rings is so pronounced. The good stuff is pretty hard and the crumbly stuff is, well pretty crumbly.
I think with practice you can get bolder and use the drawknife. It's finding what works for you, I like to use the D/knife to scrape as well as cut. With the blade upright and the bevel towards you, pushing it away gives a nlce scraping action whigh really removes or roughs up the crumbly stuff taking it right off, or making it show up better for removing with the scraper/rasp/file/whatever.
Another fave' is to hold one handle solidly agianst my thigh and push the other away, this gives very close control but with plenty of power.
Hmmm is this begining to sound silly?
I find chasing Yew rings is pretty laborious as there is not such an obvious difference between the layers and the rings are closer. If the light isn't just right then forget it, fortunately Yew isn't so fussy, presumably because the wood is more homogenous.
Del