Gushue, from St. John's, N.L., led his rink past Saskatoon's Steve Laycock (1-2) in dominating fashion, scoring two points in the final frame for a 7-3 victory in seven ends.
Howard, representing Coldwater, Ont., downed Winnipeg's William Lyburn (0-3) 8-2 in just six ends.
Brent Pierce (2-1) of New Westminster, B.C., led his rink past Peter de Cruz (1-2) of Switzerland 6-3, while Rob Fowler (2-1) of Brandon, Man., topped Team Kevin Martin (2-1) skip John Morris 7-4 in seven ends.
Jim Cotter (2-1) of Kelowna, B.C., scored four points in the sixth end and another two in the seventh to slip past Jake Higgs (1-2) of Harriston, Ont., 7-6.
The tournament is the second men's Grand Slam event of the World Curling Tour season and has a purse of $100,000.