As an example of someone who has discovered maths at a later point in my life than average, and who has (perhaps unusually?) proven the point that it is perfectly possible to study undergraduate mathematics with almost no prerequisites, I am now having to accept that fluency in mathematical techniques is in the end extremely important in the long run.
I am curious about the extent to which having a rich exposure to elementary maths techniques must influence creativity in research later on? At the moment I have taken on a full-time programming job, and I am looking for optimal methods for improving fluency in elementary maths, that could work in such a limited time frame. Any suggestions? Could it be feasible to multi-task- say, for example, practice methods of mental arithmetic at the same time as doing something else?