When to cut scion wood? Like apples - in the spring before budding. They can be stored in fridge like apple scions too.
How to identify scion wood? Identify a female tree the year before and mark it to collect scion wood the next spring. Year old growth can be identified like apple wood. You can tell females by the fact that the tree has fruited or you can learn to ID flowers. Female flowers are easy to ID. Look on the Internet for examples.
Best type of graft? Bark grafting works great and I have had cleft grafts to work well too.
When to graft in the spring? Sometime after the host tree comes out of dormancy and begins leafing out. Graft the dormant scions to the active tree. The success window in time is wide.
Be sure to brace your grafts after they start growing or the wind may break many of them off. I had this to happen a lot last year. This year I braced with cane and duct tape and didn't lose a single one. I had about 95% success rate on persimmons this year.