You're probably Doing It Wrong
So did I for a long time, until I read and re-read the rules for dishing out these points.
Whenever you fail a Fear test, there is a chance you will gain Insanity Points. Fear tests are not just from Psykers with their Fearful Auras or Deamons, it can be many things, the book gives a few examples (p233):
Disturbing (0) Viewing the scene of a gruesome murder, minor unknown supernatural or psychic phenomena—strange
lights, spectral voices, weeping statues, etc.
Frightening (–10) Meeting someone you know to be dead, being buried alive, major supernatural or psychic phenomena—
the skies raining blood, a painting forming shrieking mouths, etc.
Horrifying (–20) Sudden, shocking and inexplicable death (the man next to you on the shuttle suddenly dies, vomiting
maggots), hideous moments of revelation (finding yourself covered in blood, surrounded by bodies with a meat cleaver in
your hand and no memory of how you got there), the dead rising across a whole planet, etc.
So if you have a Psyker in your party, there is a good chance that many of his unavoidable Psychic phenomena will let you dish out IPs to everyone. And viewing scenes of gruesome murders should happen at least once every session, right? There is a reason why PCs should pick up the Jaded talent.
As for Corruption, it is a little more tricky.
Psykers tend to attract these the most, as every time they roll a Peril of the Warp, they get 1 CP. That one is easy to miss, but regardless of what the effect may be, they get 1 CP in addition to any other they may pick up as a result of Mass Posessions etc.
Warp Shock can cause corruption of you like letting your players face warp beasties, and they fail the Fear test these nasties cause. If you're going light on the deamons (as I have done, preferring more "low key" and human opponents), you will have to resort to Sorcery rituals and forbidden research to "award" CPs.