blast beats hmmm... if you would take a close look at blast beats some drummer play the blast beat with the hi hiat + the bass drum against the snare in a single stroke motion. its bass drum + hihat (or ride) alternate with the snare and played fast. take things slow and build it up from there, as this beat "burns" the foot and if ur not used to it you wont even last a stanza.
and sometimes it comes in a form of a triplet, snare + hihat + bass all the three alternates. i suggest you try them both.