The best method is to apply a small amount of the mix on the concrete surface and start spreading it evenly. If you want clean & professional looking edges, you need to use a concrete edger within 20 minutes of application.
If you allow the mixture to cure untouched, the result will be a smooth surface. This is the best outcome for a garage floor but it can be slippery when wet which means it is undesirable for walkways or patios. To prevent this, rough up the surface with strokes from a long-handled broom. Make sure this is done within 5 minutes of application or else the mixture will become too hard.
Concrete becomes harder and stronger as it cures. Companies that manufacture concrete resurfacers claim their products achieve maximum compression strength of 4,500 psi after 4 weeks and should be at 3,500 psi after one week. Of course, you don’t need to wait this long to use your concrete surface.
In most instances, you should be able to start walking on the new surface around 8 hours after application though you need to wait at least 24 hours before driving on it.