I'd like to tone down one of my flavors by adding a more mellow flavor, but I'm not sure how to make the taste even. is the only way to o this to get multi bowls?

Lots of options here.

Mix them together. Just what ever ratio you want to try.

You can layer, but put the stronger flavor on the bottom.

Also try a milder shisha. Like Nakhla
http://www.hookah-shisha.com/store/pc/vi…

You can also mix a non flavor tobacco to tone it down a bit like Nakhla Zaghoul, Nakhla Light Zaghoul, or Tangiers Cooling.

Is there a proper way to mix different flavors of shisha together w/out buying multi bowls?