Get yourself a gallon container and mix all the TF-4. It's quite long lasting; it can be reused; and there's no need to risk having inconsistent batches by trying to mix a small amount at a time. I keep two gallon-sized batches of TF-4 going at once, one for film and one for prints.
I stopped doing the PMK afterbath on the grounds that it only increases background stain and not image stain and haven't noticed any detrimental effects. When I get a chance, I'll shoot two identical negs and do one with and one without, just to be sure of that. The supposed advantage of the afterbath is improved grain masking, but I'm not sure that I see it, perhaps because I don't tend to make very big enlargements.