Addison, a seventh-round draft pick from 2015, got onto the scoresheet with an assist on Julius Nattinen's power play marker at 18:24 in the second.
The 20-year-old Brampton, ON native also added a goal to his tally at 3:48 in the third, with a laser that beat Seattle netminder Rylan Toth from the top of the circle.
Addison now has three points so far this tournament, and has found the back of the net in each of his first two games on home ice.
The Habs' ninth-overall pick from the 2016 NHL Draft, Sergachev, for his part was held off the scoresheet opposite Seattle, but finished his night with a plus-1 differential, and one shot on goal.
The Spitfires will meet the Erie Otters next, on Wednesday at 7:00 p.m.
Fellow Canadiens prospect Simon Bourque, meanwhile, will be in action when the Saint John Sea Dogs face Erie on Monday night.
Habs general manager Marc Bergevin and head coach Claude Julien were both in attendance at the WFCU Centre on Sunday.
