Attached Link: http://www.annsartgallery.com/Tutorals.html

I use a freeware program (pc only) that has all the primitives available for metaball, allows stretching and reshaping, and allows negative effects (seems like true boolean to me) then I convert to polygonal mesh and export for use in Bryce. The freeware version of Metasequoia is the one that exports. The program is undocumented and I did a couple of tuts already. Might do one on metaballs this weekend so keep an eye out.