There's several things you can do to the flesh side to make it smoother. The simplest way is to simply slick down the flesh side using a combination of coating, pressure, and friction. Apply something like gum trag, and rub with a burnishing stick until it's smooth.
You could also sand it first, depending on whether or not the back is stringy or if it's kinda soft like suede. In severe cases of the flesh side being really stringy, you may be better off by slicing the majority of the stringy leather off with a skiver.
If the back is kinda smooth, but is really hard (the 'crackly' description) it is likely a pasted back. That will benefit from sanding before slicking. You can use a variety of tools to do this, but I've found that an electric random orbital sander really speeds things up. Remember to step through the grits, ending at 400 or 600.