Need some advice about best practice approach for scheduling Anti-Virus scan using Trend Micro OfficeScan 10.6 SP2

Environment: Running 4 ESX Host with about 20 VM's (Windows Server) on each host. Each ESX host has 16 CPUs x 2.26 GHz, with 262130.80 MB of RAM.

Anti-Virus Solution: Trend Micro Enterprise Security Suite. Primarily using OfficeScan for servers.

Questions:
1. What is the best approach for scheduling a scan? When should I schedule a scan to all VMs, and how often?
2. If I run all scan at once? Will that slow down the network or use up all resources as specified above? Is what I have enough to run all scans at once, or should I set different scan schedules?
3. Is there any videos online that will show me how to do the basic administration with OfficeScan? Basically I want videos that show me how to configure Server-client (endpoints) configuration using the Office Scan web console.