[Kale]

Going for the Rule of Cool and Fun Psudo-Realism here:
You could do a forward dive (more like just fall forward onto your stomach) while bracing the shield over your head. The character would end up with the shield braced into the dirt and angled over the head and shoulders. I'd allow that to count as a 'dodge and drop' and then use the shield as cover DR. Not so great for relatively fragile medieval shields (better than nothing against mild shrapnel though), but pretty viable for a force shield. Given that your whole body would be stretched out behind the shield I'd let it work for even a medium shield, assuming that the direction of the cone attack or shrapnel came from directly forward. For something more enveloping, like fire, maybe only a large shield would be effective since the flames could curl around the edges of the shield so a medium would be too small. For a large shield instead of a dive you could 'drop' to your knees and curl into a ball behind it for similar effect. For any of these I would treat it as an all-out-Defense and require both a dodge roll and a block roll, with both benefiting from the shield's DB. Failing Dodge would mean you didn't get in position fast enough, while failing Block would mean a failure to properly brace or position the shield (although if successful the Dodge would still allow the character to have changed position in time which has implications for shrapnel to-hit rolls).