rough animation interpolation

for freestyle a animation project I am presently rendering every second frame in one session then every third frame in another, then I add in some of the “third frames” into the “second frame” batch to compile the movie…is there a way to have blender randomly render an odd numbered frame ever so often while rendering every second frame, or is there a better way to interpolation between frames less smooth while rendering

If find that when you are trying to make 3D look 2D the interpolation gives the effect away