Our flights went through Hamilton in Feb and here's what I remember.
Our flight arrived at the normal Westjet gate and as we departed the plane we were directed along a secure hallway. After a short distance there was an escalater down to a very long hallway toc US Customs. Everyone seemed to wait in the first 3 lines for customs even though there were 6, so we went farther down to an empty line. After getting your passports stamped is when you get your luggage and finish clearing customs. After going though the customs you drop off your luggage for transfer to the main terminal. After this, you have to clear security again, so make sure you don't have a bottle of water in your carry-on that you purchased on the flight, opps. After clearing security, board the tram to the main terminal and wait for your luggage again.
It was all very easy, but go to the restroom before you land, I couldn't find one until after customs.
It also only took us 30 from landing until we got to the main terminal, but we only had carry-ons.
Shayne