Some of the information above is water heater brand-specific. Since you don't mention what brand you have, I'll start from the top.
Turn off shore water and water pump. Open a faucet (hot) to relieve pressure.
Remove drain plug (Atwood) or Anode (Suburban).
Either flush out the bottom of the tank with a wand or use 6' of clear plastic hose to siphon precipitate from the bottom of the tank.
Install CORRECT DRAIN PLUG: Suburban- new or used ANODE with less than 50% erosion. Atwood- New Atwood nylon drain plug. With either, use 2 1/4 wraps of teflon tape to help seal and make it easier to remove next time.
Refill water heater. If smell persists, drain and use turkey baster, etc to add an ounce of bleach. Refill with water (open hot water faucet and let run until all air removed). Let sit for an hour. Drain and flush.