The shingles on my sheds roof are showing their age and in some places water is getting through. I spot treated the leaks with a rubber spray sealant that you may have seen on TV. Hasn't rained yet so I don't know how good, or bad, this stuff is. But, I am considering coating the entire roof with something to seal an preserve the shingles for another few years. I am considering using driveway sealer over a nylon screen; the kind used for screen doors and windows. I have about 5 gallons of drive way sealer left over from the last time I used it and enough nylon screen from a not so long ago rescreening project. Suggestions and advise will be appreciated.