Walt,
Don't tell anyone but...I've done this a few times. Yes my name is Bubba and I tune my rifles under the big oak tree out back. Works very well where the rear guide is sloppy. You can get a package of various sizes at Harbor Freight or try the electrical aisle of the big box stores. You want a tight fit. Actually if you can get one with the right thickness you want to "screw" on the spring.
Prep by cleaning and scuffing up with very coarse sandpaper. Clean again. I've actually used 3M spray adhesive on the guide, slip on the shrink tube and then shrink it on. Using this process I did my B25. Really smoothed out the shot cycle. I opened it up after a couple thousand rounds and it looked like the day I did it.
Some purists will scoff at this but unless you have a lathe and can turn custom guides what else are you going to do?
Don't over tar the spring. Excess does nothing but hurt velocity.
My 2 cents...
Bubba