Need some help, how can I determine someones draw length when i don't have a bow they can draw all the way to anchor.

Most archery shops have a draw check setup.  Taht is the best way.  The others are more of a ballpark guess than anything.  Kind of wondering though, why you are concerned about a draw length without a bow to be shot?

Arne

FITA mentions using an elastic cord presumably so they don't have the weight of the bow to contend with.

I'm sure a little creativity with a piece of wood molding/plant stake/fishing pole... could give them something to hang on to so they can be measured.

One of our club members made a handful of "bows" like this with simple string to demo to kids how to hold and draw it.