So the key here is speed. You want to speed up not only painting but the whole process. Do things in batches.
1) When cleaning up figures, do an entire box at a time. Remove all of them from the sprue.
2) With sharp knife or hot pin remove mold lines on all of them.
3) Wash the entire batch with warm water/soap. Rinse and dry.
4) Attach 3-4 figures of the same type to a tongue depressor. 4 if you can manage. This is going to be your big time saver. You pick up 4 figures at a time and paint 4 figures. You are not wasting time picking up one figure, painting it, putting it down, picking up the next etc. The second reason this is good is that you don't waste time turning each figure to paint each side. You paint all the fronts. Turn the stick. Paint all the backs. Put it down. Pick up the next. repeat. You will cut your transfer time to 1/4th.
Painting. I don't usually waste time with washes. Rather I paint on the darkest color first. Paint the higher points the base (middle) color and then highlight the highest point. Washing can be quick when it is done right. If it goes wrong, it can be a disaster.
Painting Irregulars: You want each figure to be different right? That's why they are called irregular. So, paint all the figures on one stick, exactly the same. The next stick, paint all the figures on the stick exactly the same but different from the first. You might have 6-7 different schemes in an army. Do not base until the entire army is done. Pop all of the figures off the sticks, mix well and then randomly place them on bases or in units.