Yes, Bob's method works. Check out this site's 'Top Tips' section (accessed from just under the Gscalecentral loco right at the top of the page. It was five or six years ago that I wrote the relevant tip for GSM, since then the paint has peeled due to the weather but it's no great problem to repaint.
Then again consider using leds, they don't fade and have a much longer electrical life than bulbs.