How to replace a small halogen bulb in outdoor accent fixture that my fingers barely fit into?
You need a suction cup

Electrical lighting fixtures with recessed bulbs often come with a suction cup. It's a odd device to have in the package if you don't realize it's purpose so they often get thrown away with the packaging. Fast forward a year or two and you need to change the bulb. 

That's where these come in handy
www.amazon.com 

You simply push it against the bulb and twist. They come in a variety of styles and even come with extensions to change ceiling fixtures from the floor without a ladder or stool.