I've used Badger Modelflex acrylics for years with good results. To match MTH PRR DGLE I use a mix of 4 parts Engine Black, 1 part Weathered Black, and 1 part Brunswick Green.
Pictured below is an example with my RK K4s. The pilot and cylinders repainted with the mixture described above. The rest of the model is stock MTH DGLE.