White residue on your hands could mean any number of things, depending on the underlying surface. Epoxy paint? Vinyl? Plaster? Something else?

Not sure why you were told to shock the pool -- probably because they detected some combined chlorine. Problem is, that wasn't a problem!

If you've kept your chlorine up, and haven't been using an algaecide, the CC they detected could be
  • A testing error (VERY common),
  • The result of someone having recently whizzed, or sweated a lot, in the pool.,
  • The result of using an algecide they told you to use,
  • Or something else.

Regardless, CC on outdoor pools go away very nicely by themselves WITHOUT shocking, if you just maintain reasonable chlorine levels. Shock is appropriate if you have extreme CC levels in the spring time, or are trying to get rid of bromide (Yellow Treat, etc.), ammonia (Yellow Out, etc.), algae, or what not.

High chlorine levels from shocking are unlikely to hurt anybody, but could be very hard on swimwear.

Your alkalinity is high enough -- pH+ (soda ash or sodium carbonate) increases carbonate alkalinity. Use borax instead.

Your CYA is high enough. Switch to bleach or calcium hypochlorite instead. Bleach won't increase your alkalinity or calcium, but cal hypo will.

PoolDoc