You are opening a couple of cans of worms here. Everyone has an opinion, and often not the same! Be prepared!
I have used both Mr Surfacer and Tamiya Fine Grey Primers as well as others not mentioned here (Vallejo, etc). My personal preference is the Tamiya one but Mr S is really just as good, and both are far better than the others I tried. I use the rattle can myself, where I can, as I hate cleaning primer out of my airbrush and it is so much easier just getting the can out instead of unpacking the compressor etc.
I have used Plasto putty and Mr white Putty, but in my opinion, neither are as good as Tamiya grey putty which unfortunately is not an option on your website. For fine gaps and where I do not want to lose detail I use Perfect Plastic Putty as this can be wiped down with a wet Q tip or paper towel to remove the excess - it does not bite into the plastic. However, for that same reason, it is not good for joints that may flex as it can crack and fall out.
Good luck in your search. I hope you find something that suits your needs.