I did not pull up the tools listed, but have a short answer for you. Yes you can to a great degree true up the action body, BUT you cannot true the bolt lugs without a lathe. I still think that the bushing system can give some benefit by trueing the action face and lug abutments and to some degree the action threads, especially if you also get one of those boltface truers. If you were to cut the action face and and lug abutments, lap the bolt into decent contact, and then use the bolt face truer you are going to be about as close as you can get without a lathe. Another thought would be to buy the oversized PTG bolt and use the action reaming tool.
With the amount of play in a remington, and the cocking piece induced cant, and the way they seem to shoot anyway, leads me to thinking that these actions are not as much of the total accuracy package as some believe. I have been told by an old BR shooter that so long as the barrel is good, the chamber is semi straight and the bedding is good, they will shoot. Don Geraci builds about the best shooting rifles I have ever seen, and he will only true the action face and lap the lugs. He thinks everything else is just fluff. With his track record of routinely sending 1/4 MOA remington based hunting rifles out the door I have to think he is right.
I use the fixtures at times, sometimes I true them in the lathe depending on how I feel. I have not noticed any difference in accuracy. Still if it is a confidence issue, which I feel most of what we do to these actions is, you are probably better off sending your actions to the smith. If I recall I spent about 700+ tooling up to true actions.