Looking for idiom/expression to describe an instance where one makes something seem better than it really is

Maybe the example would help to describe the expression I am looking for:

Say - a sub-par school or organization makes a promotional video, whereby they make the school look way better than it really is. They accomplished this by interviewing a few successful students, showing only the best parts of the school/classes, picking a few angles, and omitting 80% of what really represents the true situation.

I have heard the following expression, but not sure whether it's appropriate, or even phrased correctly:

Turn chicken into a chicken soup.

EDIT: actually the expression was

Make chicken salad out of chicken $#!%"

coined by Brock Lesnar. Obviously it's less befitting than others mentioned on the thread.

Solution 1:

The one I like best is polishing a turd.

Solution 2:

I would consider cherry pick and golden sample; both involve the selection of a nonrepresentative group to give the best impression.

Not precisely an idiom, but an expression that may be easy to overlook is false advertising.

Also related: spin and its derivative terms. These usually have negative connotations; compare put a spin on, spin doctors, etc.