Infil Shadow is 100% proc based. Using which abilities depends on what's triggered at the time.
Open with potency for force breach. Spin, spin, throw a rock. Use shadow strike if procced. Use breach if at 3 stacks. Use project if at 2 stacks. If project and breach are at max stacks, breach FIRST, project after. If project is at 2 stacks and shadow strike is procced, use project FIRST, shadow strike after. Use clairvoyant strike whenever nothing else is procced to build stacks for project. Use auto-attack if you don't have force for clairvoyant.