I did apply! Shortly after I sent in the supplemental app (the 1 page form along with a check), I received an email saying they had received the supp app (and I can see my check was cashed).
No portal that I'm aware of, so will presume official GREs are received unless I hear otherwise.
Are you familiar with UPS? I am not, other than what I've read of this forum, but students seem to really like it there.
Good luck!