I honestly don't do dirty bowls. But I'm biased and NEVER mix weed with tobacco.
Flavors are all up to you.
Not IMO
If it's thin foil, I usually do 2 layers. If it's Heavy Duty foil I only use 1 layer.
Punch holes like this:
IMO, dirty boles don't get me as high as a bong would.
For the bowl, place the charcoals (3 coals max) around the LIP of the bowl, not the center. Every 5 mins or so shift the coals to a new part of the foil.
When packing the bowl, lightly sprinkle the shiha in the bowl, and then pack down a tiny bit. Do this until it's flush with the lip of the bowl.