I use the putty also and prefer it to a liquid epoxy. I simply used paste shoe polish as a release agent on the barrel and scope rail. Easier to use and no mess. I found no need to sand any parts because I did not want the putty to be permanent, just fill in any gaps under the mount. The rail screws should be the attachment not the epoxy. Use non permanent 'Loc-tite' on the rails mounting screws.
One other step not mentioned is to fill the gap area between the forward end of the mount and the barrel. This gives a rock solid mount for the base, especially when large and long scopes are used. When it drys just use a black Sharpie permanent marker pen to color the epoxy.
I also make a rubber gasket for around the barrel stud for the forearm to rest against. Do not over tighten the screw on the forearm. Just snug the screw and back off a hair.
If you have a wood forearm you will find that the metal attachment at the rear is secured with two screws. This is the weakest link of the forearm because of the screw hole to grain alignment. I used the two part liquid epoxy here and in the screw holes. Really firms up the fit.
With all of this done refrain from resting the rifle on the forearm when shooting. You will find that best accuracy is obtained when resting the rifle under the metal section of the action forward of the trigger guard.
You may want to polish the chamber for ease of extraction. Use Flitz for this and go easy because you don't want to change the dimension of the chamber just polish it a little.
Another thing, remove and clean the extractor/ejector. It comes from the factory with heavy grease that can gum up quickly and give extraction problems too. Use light oil and reassemble.
Once the scope is mounted refrain from slamming the action shut. The NEF can be a reticle separator with hard closing of the action.
Have fun with your NEF,
Chris