Adding a roller truck to the tender and a wire tether to the tender is an effective way to make sure you aren't loosing power at the loco.
You may as well do a ground tether as well on an 0-4-0.
Best is a roller, but shoes and "grinders" are pretty easy to fabricate too. Automotive feeler gauges work, so do bushing/spring& wide low profile mushroom head screw/nut; head down... etc. You want it as close to the wheels&bolster pivot as possible to track more on center in curves.