Temperature for freezing media:
if you are using DMSO and the cell line is a typical lab cell line (immortal/transformed/cancer line), then you can work at room temperature (RT) with the media between RT and 37C. You can leave cells in DMSO containing media for ~ 30 min at RT without viability dropping below 90%. Then freeze at < -70C.
If you are freezing down primary cells or very finicky cells, place the media on ice and work quickly to prevent the cells "drying out" from the anti-freeze agent (DMSO etc.).
Centrifuging before counting is fine.
Remember to note the volume you took from the culture and thus centrifuged, and the volume you resuspend the cells. Then you can calculate the density of cells in the original culture.
Hope this helps you