me i like a good full flame in a pluming torch and just use the tip of flame need ,make sure wood is dry or it will crack or warp ,,, box calls i would think u should flame before tuning ,,, if calls are made already i would think before flaming them just in case they crack or warp ,,, osage is no problem just dont get realy hot ,,, chestnut never done it but have done lots white oak which iam sure would be pretty close chestnut