I use an old credit card, or wooden skewer to scrape back the carbon,
first I use a cotton bud to soak the carbon with bleach, nice and gently
not splashing it on the cylinder, after soaking I begin with an old tooth
brush to pull the carbon back away from the cylinder, put more bleach
on the toothbrush and massage in carefully, this works good for me, I
use the wooden skewer to pull the carbon closest to the cylinder away,
or an old credit card if the carbon is tougher, cut it to shape.
I steep the the spark screen in 1/2 inch of bleach in the bottom of a suitable
glass, after a few hours, I use the toothbrush to remove the dissolved soot, and
steep again if required and repeat, always works well for me, but I clean the screen
on a regular basis so its never really a lot of work and only a few hours steeping
required, I have never had to use a gas torch to clean a spark screen.
Run a different oil to cut down on that carbon, but having said that, your piston
looks like it was well protected by what ever oil you used.