I always post a link to this Khan Academy series on dimensional analysis. All med math is, is dimensional analysis - converting units. If you work through all these videos and understand the concepts, applying it will be pretty easy:
Med math is made way too complicated. I would argue that there is no need to rack your brain with the dimensional analysis. There are 4 SIMPLE formulas that can be easily committed to memory that will allow you to figure out any drug dosage and infusion rate. Learn the few basic principles that go along with these formulas and thats it. It really is that simple.