68 Bullet fender signal indicators bulb replacement (HOW?)

The smooth lenses (67 only?) can be a real chore to get loose without breaking them. Sometimes you just need to buy new lenses along with the bulbs. I've used the eraser end of a pencil to work them loose on ones that aren't corroded. Otherwise, I just cut a slot in them for a screwdriver. As for the bulbs, once the lens is off, squirt some WD40 or similar to help get the bulb broke free. A tiny screwdriver can help to work it loose. I'd use some lube on the bulb and lens threads when assembling it.