I would do a group demo first and get 19 for the price of 10. grey balls mean nothing at all. Then if you see at least 5 players you want to interview, I would skip measuring, cause the potential is probably most important. Then if you don't like at least two I would fork out on scouting in the last weeks, but then again if you can consider it, do it and do combine and demo first or do what I said earlier and some shots in the dark!
I hope it works out well!