I have done all the goof-ups possible on speed drying osage.
Here are a few, all green staves;
Staves in the attic in the summer, bark and sapwood removed and sealed in the summer, ruined by checks. Bark left on, same result.
Sealed Staves in a hot car in the summer, ruined by checks. The same for a closed up out building.
Sealed staves put in a drying box at 100 degrees, badly checked.
Here is what worked;
Reduce the stave to a bow blank let it sit at ambient M/C for a couple of weeks then put it in the hot box at 90 degrees. To be on the safe side I would put it in the box for 12 hours and out for 12 hours to stabilize, then back in the box. I would repeat this for a week then keep it in the box.
I have a moisture meter and have found when you get to 16% MC you are safe leaving the wood in the hot box just don't turn up the heat to far.
Bow blank staves dry out fairly quickly, a month should do it, with raw staves it takes a couple of years at least.
I find bow blanks dry more quickly if kept in your climate controlled house prior to a trip to the hot box.
My standard method is to cut way more osage than I can use, remove the bark and sapwood and seal with shellac. Start the stave drying process, in my case under my house. Pick a few pieces to turn into bow blanks for faster drying, put the rest in the on deck circle. As I make a bow out of wood that has dried I move more to my shop to cut into bow blanks. So, it is under my house, out to the shop, bow blank then bow. With the amount of usage I have it may take 10 years for a piece to go from cut green to a bow, I have bow blanks in my shop that have been there for 3 years, none of them speed dried.
The on deck circle;
