Done 3 - on the back side is the side where the Sheriff needs to sign...put little stickers pointing out EVERYWHERE they need to sign/put in info. In the section where it has your full name on the back, you can fill it in yourself. Just make sure the Sheriff or his designee knows where to sign and fill in other data.
Otherwise...that was really all I did; follow the thread in the NFA forum. Cross all the Ts and dot all the Is, get your photos beforehand, bring cash to pay the fingerprint fees, make sure you use the ATF fingerprint cards...don't use a stupid reason on the form, like "for the zombie apocalypse"; they'll send it back and ask for a proper reason ("for collecting and all other lawful purposes" is what I used)...you should be ok.
To smooth things along, bring a large self-addressed and stamped envelope to your Sheriff's office with the forms; mine usually takes a couple days to sign it then mails the resulting forms to you. Dropping it off with a pre-addressed and pre-paid-for document (large, page-size) envelope really does help a bit