Then mask it off in place and paint lengths of one rail at a time - starting with the furthest outer rail from you, to the center, than to the closest outer rail. In this way, you do not have to remask a lot. You can leave the step about wiping down the rails with thinner until last - even if it takes a span of days, as the paint comes right off the rails.
There are no open ends to plug on O27 metal ties, in accordance with the overall superiority of O27 tubular track to O31.
Be cautious about superelevating toy-train curves. It can exacerbate the problem of pulling cars off the track on curves. I have suggested negative superelevation as a possible cure but have never tried it.
You can cut a bunch of ties to the required two-inch length at one time by stacking the Popsicle sticks.
Four 3/8-inch Popsicle sticks look good between each pair of metal ties.
I am also using 027 Lionel tubular track and I purchased a bunch of plastic ties from 3R plastics, they are molded to look like real wood ties and they look great. I will take a picture tonight and post it later so you can see what I am talking about.
I am also a scale railroad modeler, in HO currently. We generally lay our track (secure) and spray paint it (all one color), ballast, and then clean the tops of the rails. If you look at photos of real railroad track, the sides of the rail are generally very close to the color of the ties in most cases. On some branch lines and sidings the rail sides may be more of a rust color compared to the brown of the ties though. This will certainly save a lot of masking time and result in even more realistic looking track. Floquil “Rail Brown” is the color I use most for this. Here’s a random photo: