Originally Posted by: jarkko.eklund However, I haven't figured out a good way to count 16th note triplets, which would help me to improve especially practicing sweep picking arpeggios.

Counting every subdivision gets really tricky when there are lots of them & the tempo is fast.

I typically count 1/16th note triplets as 1-6, then change the 1s with the beat count. So in 4/4 time.

1-2-3-4-5-6, 2-2-3-4-5-6, 3-2-3-4-5-6, 4-2-3-4-5-6.

But when things get really fast it gets hard if not impossible to say that stuff. :) Best of success!