I hope you mean shine to bair as a combo move together. To do it, input a shine, turnaround, and either tap jump or use cstick up to jump, and then input a bair. It’s pretty difficult to do since it’s DI dependent, and can be also used to counter floaties like Jiggs who SDI up often. The trickiest part is that you have to hit the opponents with the upper portion of the shine hitbox in order for this to work.
My best bet would be to just practice by up throwing a CPU at high percents and doing shine bair in them. You should be able to land it as long as you are fast enough out of shine.
Only reason why I even know that is because I mained fox for like 3 months.