As Bill K said above, the filters work great for most applications. Bulbs also work pretty well. I have had good luck with both #432 (screw base) or #1445 (bayonet). Both are 18 volt rated and last quite well in my experience. You can pick them and the bases up at any electronic jobber, or Radio Shack in a pinch. Wire one across each TIU output for starters, or MTH star terminal strip input, if you use them.
Rod