Should be the same as for crossing border anywhere. You will need paperwork from RCMP, including temporary gun permit and authorization to transport (ATT). Unloaded gun is locked in a case with trigger lock put on. All magazines must be permanently pinned to 10 rounds max.
I believe Roy Neal helped a few people from Detroit area to get the paperwork during last few years.
I have been to Canada before via Detroit with Roy a few times and understand those rules. The issue is traveling through NY to get to the border. Their mag rules are more stringent.
I have has issues at US Customs and one of my teamates had issues with NY State Police even before the Unsafe Act.