I've been just plugging in a long extension cord with a 30A to 15A Long Adapter Cord from WALMART into an unused 20AMP SERVICE 120VAC receptacle that was installed in my garage for an Air Compressor at one time... This has its own 20A Circuit Breaker in the power panel in the Garage. I am always checking my connection that is laying on the ground to make sure it is never getting hot on me...
I probably should do the same thing and run it to the outside of garage like you did... Nice Job...
I like these two helpful drawings on GOOGLE showing how they would be wired up for the 30A SERVICE CONNECTION...
Typical 50A - 30A Campground PEDESTAL setup wiring.
Google Image
Google Image
Roy Ken