Verb
smooth down (third-person singular simple present smooths down, present participle smoothing down, simple past and past participle smoothed down)
(transitive, idiomatic) To render smooth, to remove roughness from
She smoothed her nails down with a file.
You can also smooth down the part of the beret that sits over your ear for a variation of this look. Source: Internet
Use a rubber spatula to smooth down the top. Source: Internet