Bido,
Get yourself a set or three of these:
http://www.motionpro.com/motorcycle/tools/tappet_feeler_gauges/and you will prolly change your mind about the easiest way to adjust tappets.
When I first got my 550, I too was concerned that feeler gauges, even the ones with the 45-degree bend, simply wouldn't fit into the hole under a tappet cover. I was further confused when I started to read this forum. People refereed to tappet adjustment as simple.
Then someone turned me on to the right tool!
Guess it's taking me a bit to Learn the differences between automotive and motorcycle repair. The concepts are the same, but the tools and techniques can differ greatly!