This is something you can hear quite often about Project Management Techniques: they can solve problems, especially “not measurable” aspects of a project.
I see a basic problem here: how can you manage something you don’t know?
It is not a technique problem, for techniques can’t be a solution for basic problems.
Things are measurable = you know what you want (the product), therefore you have defined all that you need to obtain such product.
This is the first thing you need to do: define exactly what you want (i.e., the product), so that you can organize things.
Mind, a product can be an event, just to give an example.
If one is not operating this way, he/she is not doing project management; besides, he/she is probably going to get a mess.
I would advise you this link: even if it is an historical article, it is very enlightening, in particular the “Napoleon was a Project Manager” chapter.