A useful guideline to know when you can start up your trowel, is when the operator can stand on the concrete surface, and leave footprints about 1/8”-1/4” in depth and you can walk on it firmly without the top layer sticking to your boots it is ready to power float.

Do I need to trowel concrete?

Trowel the surface

Float the concrete when you're done grooving and edging (Photo 6). ... You may have to bear down on the float if the concrete is starting to harden. You'll be surprised that with enough scrubbing you'll be able to bring a slurry to the surface of even a fairly hard slab.

When should you Powerfloat?

A rough guide for considering when to begin power floating is when walking on the surface leaves indentations of 3-4 mm. If the concrete is too wet the machine will tear up the surface, and if it is too dry, it will not be possible to trim high spots or fill low spots effectively.