Then I have made special inserts for the swinging buckets in a standard clinical centrifuge whose buckets normally hold 15ml conical tubes, so that I can hold the 1.5ml Eppendorf tubes. I spin 'em at top speed (3000RPM) for 5 min to get viruses down onto the coverslips. (Interesting, tap 2 or 1000 RPM brings down cells normally during reculturing, yet the cells seem unscathed by the 3X added G's needed to get viruses down onto them).
The viruses have been freshly trypsinized, quenched with 10% serum, spun down at 14K for 15 min, and resuspended in Ringers' by a good 30 sec of sonication, just before the spinoculation.
The spinning is done at room temp, then the coverslips are removed from the Eppendorf tubes and placed in warm Ringers for 5 min before EM-prepping.