Trust rules vary by state so I can only elaborate on rules applicable to my state SC. By setting up a trust I was able to name myself and my wife as co-trustees. There are several benefits to a trust but again, rules vary by state. In SC:
1) My wife or I can have possession of any NFA item registered in the trust. If my wife wants to take the suppressor etc. to the range without me she will be allowed.
2) I did not have to submit fingerprints or request a CLEO signoff to complete the form 4. The CLEO sign-off is a large benefit as one never knows if the next elected sheriff will be NFA friendly.
3) No future registrations fees. I am the settlor of the trust in that the life of the trust is tied to my lifespan. When I die my wife will have to set up another trust in which she is Settlor but all of the guns can transfer into that trust without paying the $200 stamp per item.
There may be other things that I am missing but those were the big items for me. Avoid any advice to write your own trust using Willmaker or similar software and seek legal council of a qualified gun trust lawyer in your state. My local lawyer charged $200 and I can guarantee you that I left with more than $200 worth of solid information.