Electrical – What work is needed in changing a two prong to a three prong outlet

If you're working with leftover materials, you can surely pull 12/2 nonmetallic sheathed cable through conduit. You'll want to avoid lots of bends and long runs, as it will make pulling the cable more difficult.

If you're up for buying some wire, you might find it easier to pull single conductors through the conduit. Stranded wire is often easier to pull through conduit, though you might find it more difficult to terminate at devices. You could pick up a 25' roll of #12 THHN stranded copper, for about $8.00. You'll want 3, one black (ungrounded "hot"), one white (grounded "neutral"), and one green (grounding).

Since you're using a 15 ampere cord to supply power, you can use 14 gauge wiring instead of 12. If you're buying new wire, this could save you some money. If you're using materials you already have on hand, there's no problem using larger gauge wire than what's required.

Installing UL listed power strips is a safer bet. If you know what you're doing, there's nothing wrong with a custom solution.

Wire from the panel to the closest outlet. Use Ratchet Freak's recommendation of using a GFCI since this has a potential to become a wet location. Put the GFCI at the first outlet location and wire the line/feed side of the outlet to the wire running from the panel. Add a second wire that will chain the second outlet to this outlet. On the GFCI, the second wire will attach to the load side of the outlet and the other end will wire to a normal outlet.

For a 20 amp circuit, you will be using at minimum 12 gauge wire. Make sure the wires are anchored to the studs outside the box and they are running through the middle of the studs to protect from screws/nails. If you have to notch a stud to run the wires, make sure you add a nail plate over the notch.