Squeeking brakes are caused by the pads vibrating at high speed. Many people find that the problem can be reduced by thoroughly flushing the pads with water. You might also find that adding copper grease to the rear of the pads can reduce the noise - but this should be done by a brake specialist.
AFAIK, brake seal is NOT a sign of worn pads though.
There's been a thead about this before - have a search through the forum listings.