I have never installed drywall before and I was wondering if I can use my regular cordless Black and Decker drill to drill drywall screws or do I need a special drill ??

I installed drywall to a rental unit - cathedral ceilings - Tenant smokes heavily and burns candles all the time (don't suggest eviction, she's an inlaw) There's a film on sheetrock - most notably the upper seams and screw heads are visible and look like black dots - you can't feel them - they're not popping - I'ts been suggested (by my brother a sheetrocker for some 25 years) that its a reaction to the wax from candle wicks and the excessive smoking. A contractor I know said he had this same problem caused by a tenant and sued them for it (and won). You can actully feel the film - and trying to wipe with a damp rag just "smears" the film. I'm hesitant to repaint as I feel the condition will continue as long as she's there, but hate to see the home in this condition. Will KILZ or a similar product cover this? It's also been suggested that I use a product called fire brick (which I've never heard of) and "sand walls" with it.