@Judd nailed it in the above post. I'll try to give a step by step guide with pics for a little more detail.
With the new eForms changes its very easy if you're in the same state. If its out of state the same process works, just has to go to an FFL/SOT in the seller's state first.
The SELLER needs to login to the eForms account then start a new Form 4. You'll see this screen. This is who the suppressor is being sold by/coming from. Select whichever one is appropriate.
The next couple pages will be the seller filling out their info. Then you get to the screen for the transferee (buyer). If you're buying it on your trust, you'll need some additional info and forms vs as an individual.
If trust, click trust and fill out the name and address for the trust. Next will be where you add responsible persons.
Click add responsible person. You'll have to do one for each RP on the trust.
Fill out all the info. It will make life easy if you have electronic prints. You will also need a 5320.23 for each responsible person. I recommend National Gun Trusts and their
5320.23 generator. These MUST be signed in wet ink then scanned to be uploaded. You cannot sign electronically.
Next will be your CLEO information.
Then you have to add a firearm. eForms now has "inventory" so it knows what NFA items you have. This is why the seller has to do this, the item they are selling is in their inventory and they will choose it from there. There are multiple ways for them to search for it.
Next is electronic documentation. This is where you will upload your trust info.
Then you verify all of the info and certify and done. Then you just sit back and wait for it to be approved. Fairly simple process, just make sure you have all of the info, forms, trust, and pictures ready to go before starting.