First form that is overlooked a lot is the Certificate of Compliance. This form is signed by the applicant and just promises the ATF that the applicant is a US citizen. Only 1 copy is required with application. Filling out is self-explaintory with the template. Even though the Trust is an entity, the trustee still must fill out & sign this form.
The Form 1 template is self-explaintory, but just be sure of a few items before submitting. First, block 2. make sure that the "Corporation" box is checked. Do NOT check "Individual" for a Trust. 4.c. (caliber) don't use "multi", it must be a specific caliber. 4.e. (length of barrel) don't use a range like 7.5"-14.5" as the ATF will send the form back. You can swap uppers legally as long as the applicant retains the original that is registered on the form and can be installed. Changes can be made as long as they are TEMPORARY and can be changed WITHOUT tools. 4.f. (length overall) use the shortest length if there is a collapsible stock.
The back is very easy, just sign box 9. with applicant's name and "Trustee" or "Settlor", what ever that person is called in the Trust and print out that information in block 10. That is it for the back of the form as no photographs, fingerprints and CLEO signoff are needed. The Form 1 MUST be submitted in duplicate and the form MUST be printed front to back. The ATF WON'T accept forms with page 1 and page 2 on seperate pieces of paper. A COPY of the Trust (not the original as it won't be returned) MUST be included along with a copy of Schedule A (Trust assets) and Schedule B (beneficiaries) or the ATF will return the application.