Simple feathering will do via the Refine Edge effect, masks' native feathering, blurring the pre-composed mattes and a million other things combined with some basic color corrections. Naturally you just have to learn how to do it and well, to be honest, it would be good if you actually sat down to learn these techniques and read the help. I know this sounds rude, but you seem to be under the mistaken impression that everything can be done with a stroke of the Rotobrush and then get yourself into a pinch because using the RB is the wrong method for many of your use cases.
for instance in this youtube video Winter is Trumping - YouTube ,
thanks you for the youtube link. he is very good
so after ive created some sort of mask, what are some standard ways of blending that mask in with the surrounding
technically speaking it's not the blending of the "mask", but the blending of the image. if your mask is precisely at the edges of the image, with the right amount of feather, then your mask is o.k and now have to color match the pixels to match the background. what you are looking for is creating a successful composite. the compositing process is an art form that involves careful selection, color matching, tracking and other techniques and tricks - all to blend images from different sources together to create an illusion they are all part of the same scene: Compositing - Wikipedia
if you are into compositing in Ae, I would recommend you take a look at Mark Christiansen's Compositing series at Lynda.com. it will go through all the stages to create a successful composite by one of the VFX Masters of Ae.