St-Gelais, of Saint-Felicien, Que., won the women's 500-metre and 1,500-metre events while Hamelin, the 2014 Winter Olympic champion in the 1,500, captured both men's races at the same distances.
St-Gelais edged Kasandra Bradette, also of Saint-Felicien, at the line to win the 500-metre race. Valerie Maltais of La Baie, Que., was third. Maltais was second in the 1,500-metre event with Bradette taking third.
"I had two good times in the (500) heats but in the final I used a strategy that almost backfired on me," St-Gelais said after winning by .009 seconds. "I wanted to lead the group but it almost cost me and I barely won.
"The experience gave me the win."
St-Gelais said she came into the weekend lacking confidence in the 1,500 and was pleased it turned out so well.
"I would like to be better at this distance," St-Gelais said. "It all starts by winning here and that will give me confidence."
Samuel Girard of Ferland-Boileau, Que., and Patrick Duffy of Oakville, Ont., were second and third, respectively in both men's races.
Hamelin was happy with his 500-metre efforts.
"It was my first competition since the world championships in March and I had three races under 41 (seconds). It went really well. I'm encouraged for my first race in a few months."