After using all continues, the game counts down from ten to zero. Press Triangle + Select + Start during the countdown for five more continues.
Highlight 'Start' and press press Up/Left + Circle + Select. This will bring up a level selection screen.
Pause the game, hold Triangle + R2 and resume.
Pause the game, hold Triangle + L2 and resume.
Thanks to Revolution readers Wes East, Josh Miller, Marco de Guzman, and Mario Coleman!