Have a trust set up.
My son is in it.
He is moving to TX or VA.
Can my trust transfer to him as an individual?

As I understand it - if your son is a co-trustee, he can be in possession of the NFA items on the trust. Therefore, you don't need to do a transfer to your son. Transferring any NFA item (either from individual to trust, or trust to individual) requires a $200 stamp and another wait on the ATF approval.

If it's a suppressor, you don't need to file a 5320.20, but some still do. If it's something like an SBR, make sure to file a 5320.20. You can temporarily transfer an NFA item on the form for up to 1 calendar year. Approval for this form usually is about 6 weeks.

I'm sure someone will chime in shortly if I'm missing anything.

I'd just 5320.20 it to him into wherever his ends up and repeat yearly, assuming its a short move.

If it's a longer move, I suggest you consult an NFA friendly attorney about the best way to do things.