be, feel, look
become
make sth, wear sth
The steps had been worn smooth by the thousands of passing feet.

sand sth
The surface should be sanded smooth.

extremely, fairly, very, etc.
beautifully, exceptionally
her beautifully smooth complexion

completely, perfectly
silky, velvety
This cream makes even the roughest hands silky smooth.

almost
deceptively
the deceptively smooth surface of the glacier

be, look, seem
become

extremely, fairly, very, etc.
a fairly smooth transition to democracy

incredibly, particularly, remarkably
The project got off to a remarkably smooth start.

surprisingly
completely
not always, not entirely
The process of negotiation was not entirely smooth.

Smooth is used with these nouns:
arc, batter, cheek, chest, chin, coat, complexion, consistency, crossing, curve, custard, distribution, dough, edge, face, finish, flesh, flight, floor, flow, forehead, grain, implementation, landing, marble, motion, move, movement, muscle, operation, operator, passage, paste, progression, ride, road, rock, running, sauce, shape, shave, skin, slope, stone, stroke, surface, taste, texture, transfer, transition, voice, wood