Is electric drill the answer with small plastic defects placed in tight areas?

In the oval space where the 1/72 scale Extratech M4 Sherman tank's gun barrel is to be placed exist a large bubbled area, a glob just sitting there where the oval space should be smoothed so that a tiny sphere like object - namely the end piece of the 75mm gun - is to be fitted. It's frustrating but this was bound to happen. Now, I'm not going in there to try and cut that blob out. I don't have the crafting skills with a blade to do it. I'll tear up the mantelet if I attempt to do so. Therefore, does anyone out there know a decent solution to this problem? The quick fix is not going to be used anymore. That I do know. Again, I ask, does anyone know how to best clean up a model when the mold includes such bubbled areas that would obstruct the construction process? I have a feeling that a small electrical drill is the answer. Can anyone recommend me a product? I'd be grateful. What's its name? What's the price? I've been putting these things together for years - and knew one day that'd come to this. Now I'm ready to take that step. I have the simple hand-operated drills, but know my own talent level. My hands are steady, but not steady enough. That hand drill will slip and create all sorts of damage. It's not the option with this Sherman's M34A1 mantelet that has like a tumor of plastic mess on top of the hollowed oval space that will incorporate the 75mm gun. Anyone's help would be appreciated. Thanks.