No problem at all
have you tried making the form as a survey? that doesn't require you to specify a case for it, or select one. however you are not going to be updating any cases with any information and the only way to get this data is through a form download on CommCareHQ via any of the available methods.
as for pulling a property of a case that was selected in a multi-select in a form, i'm using this code in one of my apps
concat(instance('casedb')/casedb/case[selected(#form/enroll/session_enrolled, @case_id)]/start_time)
i'm basically using the concat function to concat 1 node. so, it's like using the "=" operator in affect. the reason i'm using it is in order to capture any potential errors that the expression might throw. i would probably return a blank in that case instead of throwing an error. using an "=" operator can often confuse CommCare, even if it is only looking at one node.
what this code does is bring back the start time of session that participants were enrolling in and then show it to the user on their screen. the reason this code returns what i expect it to is because i'm leveraging the "selected" function. it's going to return a false if the "@case" its evaluating from casedb is not equal to the session_enrolled which is also a case ID. but it comes from the form, not from the database.
in your scenario, in place of "session_enrolled" you will have to replace it with the form element that contains the "farmers" that you were talking about. the same expression should work. however, it'll just spit the names out next to each other. replace "Concat" with "Join" and add a
,","
before the ) sign at the end. this will create a comma separated list of names that even if not in the same order as selected in the form, at least contains all the names of the individuals that were in attendance.
I just personally think that it's a lot of processing load to put on a phone, for a result that you will likely use an actual computer to get any value out of 
Mazz