repainting window lintel

The roofer put on a new roof last year. He said he was going to cut back the wall shingles so there'd be a gap between them and the roof - I think the roof shingles get wet and the siding just soaks it up. Can't be good for the siding or the house, right? He never did that / he didn't do a bunch of things he said he was going to do... I don't want him back. Would you cut those siding shingles back? How would you do it without hurting the flashing behind it? I envision a dremel type tool. Or is there something like a circular saw that you can control how far the blade sticks out? I'll get a measure of the thickness of the siding and then cut a fraction if an inch less than that, and hopefully the shingle will snap on that cut line? THANKS!

My siding needs cleaning. My research on the internet produced the advice that I should use an oxygen based bleach followed by pressure washing with a product made for siding. I have tried that on two separate occasions...once about a year ago and then on my vinyl sided back porch. I used oxygen liquid bleach (a laundry product) about a year ago and found it was not all that good at bleaching/cleaning so I switched to a strong concentration of chlorine bleach...which did much better. Today, I used oxygen bleach (50-50 with water), on the back porch followed by pressure washing with siding cleaner. Again, it did not do so well. There must be something better...I do not want to use chlorine bleach on my back porch due to the problems inherent in its use...smell, bio-hazard, etc. So, what REALLY works on White vinyl siding? I am too old to scrub it by hand.