The antonyms for "getting down cold" can be expressed in many ways, depending on the context. If we are talking about a task or activity, the opposite of "getting down cold" might be doing something haphazardly or without sufficient preparation. Another antonym could be to perform the task inaccurately, incompletely or ineffectively. In terms of feeling confident, the antonym could be feeling uncertain, anxious, or doubtful. To have no familiarity with something could be an antonym of "getting down cold". The opposite of being well-versed on a topic could be being unaware, uninformed, or ignorant. However, in any situation, the opposite of "getting down cold" would be to not have a good understanding or mastery of something.