I usually try to split my staves the same day I cut the tree, then seal ends good. I leave the bark on for a couple months to let it dry out slowly and 'naturally'. After a couple months I de-bark and usually apply a couple coats of paint.
When was the wood cut? and you're leaving it outdoors to dry, right? (bringing a stave inside in the winter, even if its partially dried can bring unexpected and unwanted changes due to the warm dry furnace air).
JMO-- others have other methods