Auxiliary belt squeal

I drive a Ford Fiesta mk7.5 2013 with the
stretchy auxiliary belt, some story behind it
but hope someone can help.

I noticed the car squealed when holding
certain revs while driving, at exactly the same
position regardless of what gear I was in, it
was a small squeal but annoyed me in the
back of my head while driving, I sprayed
dressing spray on it which muted the noise
temporarily. It then came back so I decide to
purchase a new belt (non genuine) and now
whenever I start the car in the cold or wet it
screams VERY loud for say 30 seconds until
the car has got to its operating temperature, I
have tried to diagnose this by seeing if it
squeaks with the air con on, turning the air
con off and on did make it squeal and stop
squealing but then also without the a/c on it
would squeal with a large amount of
consumers on for example the heated
screens, wipers, headlights and radio. Does
having a genuine belt affect this? Should I
have cleaned the pulleys before putting on
the new belt as the dressing could have
fouled? Any advice would be appreciated!
Would it be good to get a genuine belt clean
the pulleys and then place the new genuine
belt on?