I bought just a couple of individual Toyota-sized taps that I needed from Grainger. They have been super useful for cleaning up hardtop bolt holes, etc. The quick version of 'how to use a tap' is to:
Drill/have the correct size hole.
Get the correct style tap (bottoming or one of the other two types) with the correct pitch.
Coat the tap with cutting oil (I sometimes use anti-sieze)
Screw the tap 1/4-1/2 turn, and back it off.
Repeat - screw in, back off, etc.
Remove tap regularly (every 1-2 turns), wipe off metal bits, re-oil, and restart in hole.
The slots cut in the side of a tap allow the waste products to get out of the threads.
The goal is to not hurry, and to keep the tap clean and well lubed. Many tap handles are awkward and you'll use a small adjustable wrench at times to turn the tap. Do not overtap and overdo this, or you'll have a wobbly hole - just clean up the threads as little as you need to.
As for JIS fasteners, you can buy a $10 package of them (a 6"x9" plastic box labeled JIS Fasteners) at Advance Auto or Autozone. After you part out a few Toyotas, however, you'll be drowning in JIS fasteners ;-)
Colo Springs, CO