Well, we're here talking about rather rough surface with approximate shape and usually headlining cloth is thick with foam base, so that doesn't really matter - even errors with too much glue will likely won't be noticeable, unless the glue reach surface of cloth. When I was gluing thin cloth to mk2 golf fiberglass door trims, it was slightly different, with thin cloth too much glue errors could become visible, but it's easy to prevent, and in that case bigger problem was not very flat shape of that trim itself...
