Non-ghosting bulbs have a resistor in them, so they don't illuminate at all until the voltage reaches around 2-3v (which solves the problem of flickering in a bulb that should be off...generally a problem in inserts). If the issue is that inserts are briefly flickering when you flip, these will solve your problem. http://www.cometpinball.com/category-s/1819.htm

There is another type of bulb that goes one step further. Flux bulbs have a capacitor in them, so they briefly hold a charge if the voltage drops (which should solve the problem of flickering when the bulb is supposed to be lit solidly). They're expensive though, roughly $1 more per bulb, and you'll see them listed as well at the link above. You probably wouldn't need these in your case, but I thought it was worth mentioning.