Go to Harbor Freight and get a laser thermometer ($30 or so)
Don't worry, you will find other uses for it (cooking, working on your car, checking the fridge or A/C etc)
When you think you are smelling something, point that thermometer at every outlet and switch. It might help to take the cover off but don't go in any farther. If you find a hot spot, call the electrician back and tell him what you found.