Buy a good cabinet scraper to start and then keep it super sharp, you should be able to 'wipe' paper thin shavings off with just one hand and very little pressure. Sharpening cabinet scrapers properly is a bit of an art
Dean Torges has a great chaprter on it in his book Hunting the Osage Bow - it's the best description of the process i've read.
As for using it do as the others have said. Also if you do get any chatter then stop immediately and use a file to flatten off the high spots.
Also as you say those staves won't be dry. The 3 months with the bark on will have made little difference to the moisture content. Try and get your ring chased and then rough out to floor tiller. It will dry a lot quicker then with less chance of checks forming.