Hi,
With Hiero, when you save a .fnt file (File > Save BmFont text file), it saves pngs in the same directory automatically. You can use these directly in 2D TOolkit, as long as you observe the note below -
You should switch to glyph cache and change "Page width" and "Page height" to a larger number so it fits everything into one texture to be compatible with 2D Toolkit, but otherwise it should just work.
unikron