Yes, "practice" works as a verb here. Technically, that makes "bulk" an adverb - "to practice in bulk".
Or, if you understand "bulk practice" as a compound noun, it's been put in a verb position, and so we somehow accept it as a verb. You've probably seen that English does this quite often with nouns.
This is a slightly uncommon way of expressing the idea, but it seems to be typical of "marketing-speak".