Last month I was installing some decorative molding and after trying to pound a small finishing nail into angled molding and leaving indentations from my hammer and still not getting the nail flat I decided to improvise.
I opened the kitchen 'junk' drawer that was right in front of me and swished my hand around looking for something.. anything (!) that I could use. Then I spied it! A flat head nail. It's just a penny nail but I grabbed it and used the flat head to lay against the finishing nail and tapped the smaller end with the hammer to hammer my nail in.
To finish it off and 'sink' the nail into the molding so I could fill with a little wood putty and repaint, I turned the flat head penny nail around, put the smaller end on the nail and tapped the flat end with my hammer. The small sized nail end tapped the finishing nail right into place.
I finished my entire kitchen this way and didn't have to run to the hardware store to purchase anything - now that's in anyone's frugal budget!