Plastic trucks on rolling stock and Micro Engineering ties are both cast in hard engineering plastic (the same stuff as is used on diesel handrails nowadays and many other details which might be better done in metal
). That's why paint won't stick to it, nor will ca or other common adhesives. Even solvent-type paints or cement have little grip, and it's certainly not a permanent one.
Scrubbing with an abrasive cleaner will improve adhesion, and when I remember to do it, sandblasting freight car trucks, using baking soda as a blasting medium, helps to make paint stick better.
I recall reading somewhere that soaking plastic trucks and other such smaller items in alcohol for about a week will remove the mould release agent which is supposedly the culprit causing the slipperiness, but have not tried it. Washing engineering plastic with dish detergent seems to have no noticeable effect, but it works very well on the softer styrene used for buildings and rolling stock.
As for paints, old Floquil (the lacquer-based one, not the latest mineral spirit-based version) will deal with the residual oil left on rail from the drawing process, but I opted to use PollyScale on my rails because of the lower odour. PollyScale paint dries very quickly, but it takes longer (24 hours, at least) to cure and it's very likely that it would be even tougher after a week or so. I brush-painted all of my track using PollyScale and a 1/2" brush with relatively stiff bristles. This eliminates the need for masking, creates no overspray (that paint which goes beyond what you're trying to paint and often beyond the masking tape, too). Much of that overspray is dry before it lands, and that is what's known as dust. You will have many opportunities in the future to revisit it.
Brush-painting rail is a very simple operation, and requires almost no preparation and very little clean-up, so you can paint anytime you have five or ten minutes to spare. Turnouts, of course, take a little longer, but nowhere near as long as it would take to mask and spray. Using PollyScale, I generally paint 10' or 12' of track at a time (both sides of both rails - even on a shelf-type layout, there may be opportunities for photos taken from the "wrong" side of the tracks). Don't worry about paint on the ties, tie plates, or spikes, as the metal parts all rusted on the prototype and that rust also bleeds onto the ties and ballast - this is not fine art. After painting that length of track, I used a dry rag over my fingertips to wipe the dry but not hardened paint from the rail tops. You may be surprised, but this is enjoyable and relaxing work, and is probably the operation which will give you more "bang for your buck" than any other you will do on your layout. Closely following that is ballasting, but that's another topic.
As for PollyScale becoming tougher with time, I've found that to be true and no longer use Floquil even for painting brass steam locomotives. The original Floquil (square bottle) was a tough paint, but PollyScale is even better, in my opinion.
Painting ME ties presents the same problems, and while you could sandblast the track before laying it, I think that PollyScale applied just before ballasting may be the simplest option. Ties are not normally touched once the track is in place, and unless you have frequent derailments, the paint will likely remain in place.
Wayne