Could someone learn to lay tefillin just from watching another person do it, or would he need to try it one or more times himself before he gets it?
Also...on the scale of 1 = no big, and 10 = your name should be blotted out for even thinking of it...how sacrilegious would it be for a (Jewish) Potterverse wizard to use tefillin as a Portkey?
Google searches: tefillin
ETA: Thanks to everyone who commented! You've not only answered my question, but given me lots of new ideas.