Why not just do it right ?, most garages are easy to add New circuits,if you have the room in the breaker panel for new breakers.
They make many types of breakers now days, dual pickup off one lug in the panel if you are short on space or opening.(don't put the breakers on the same side in the panel, use the left side lug and the right side lug)(use 20 amp. breakers)
Drop cords are never a good way to go,,,,
if you can help it.
For temp service or to run a tool out side the shop, ok some times but most don't use one that can take on the load....or to say the cable size is to small,don't use anything over 25ft. max. for most power tools.
Stop by HomeDepot/Ace Hardware/or ? and have a look around or ask a sales person to help you find the Right breaker(s) for your panel.(write down the Mfg. and model number b/4 you go to pick them up)
Also ask albout a wire snake it will let you pull the wires into the shop.
Just a note,,,don't put two wires into one breaker, if you don't want to take on this easy job ask a mate to give you a hand or a license elec. tech.