most efficient and quickest way i have done it is going through Vermont
Drive to Vermont airport and fly in to new york. Total time door to door is around 5 hours on the rough from my door in montreal to door on 63rd and 3rd. Flights are around 130-160$ round trip and the drive is nice and easy.
It also stops la LA guardia which is a MUCH closer cab (and less traffic) ride than JFK.
Dont cheap out on the hotel btw. Rent an appartement instead if u can there are some prime units down there just have to know which areas to be in!
Hope this helps but i have done the train. rideshare, driving alone, plane from mtl and really best way is through VT.