I, too, have found these inspectors to be entireley reasonable. I generally check off the "food" box and have a brief discussion with them about what I have. They rarely send us for secondary, but on occasion they send our stuff through a special X-Ray like device to see what's inside. We're always careful to only bring back stuff that's allowed. For example, if bringing back cheese it can only be hard cheese so I write that on the form so they know that I know the rules.

With regard to being on a farm, etc. you may wish to write on the form (next to the box) exactly where you were (ie "sheep farm") so they can make an educated decision about sending you to secondary rather than just sending you there because you checked the box.