When to use denodeify/nfbind vs nfcall/ninvoke
Mongoose (at least in the last year or so) already returns promises that are Promises/A+ spec complaint.
You don't need to wrap them in Q promises unless you have to. Q, being promises/A+ complaint itself will gladly consume these promises and interop with them for you.
You can, for example use Q.all on three calls of find(...).exec().
Q.all([ User.find({route: foo}).exec(), // Q will detect that the values are 'thenable' User.find({route: bar}).exec(), // and will automatically assimilate them into a User.find({route: baz}).exec() // Q promise on its own. No explicit action needed.]).spread(function(res1,res2,res3){ // access results.});