What yeahok said is good information.
The tea isn't THAT bad, but still quite unpleasurable. If you boil it down enough, you can get it to the size of a standard shot (50 ml). Or you can try adding sugar and/or honey to the tea to give it a better, less bitter, taste.
Another thing to do is trying adding small amounts of caffeine
to you dose. It will help to speed up digestion. But only use a little bit as you wouldn't want to over power the effects of the kratom
with a caffeine high.
Lastly, you could try exercising more. Especially aerobic exercise will start upping your metabolic rate, thus increasing how quickly your body processing everything you put in it.
*Side note, source discussion isn't allowed here, and although I am sure every kratom user has heard of the source you mention, I would suggest editing it out