An honest sharing of knowledge empowers us all.
As much as I'd like to take credit for the masking technique described above, it's been around longer than I've been in the business...It was shown to me by aircraft painters, specifically model aircraft, where fine, straight cuts are integral to a good look. I simply adapted it for full-scale house painting, and though somewhat more time consuming, for those without the steady hand that comes from years of experience, it does make for very professional lines...
It is a great advice about "the perfect paint line". Sometimes I get the painting done by a professional as it looks better. But learning tricks like this makes me able to give a professional paint job while I save loads of money.
I modified the post to make it a bit more clear.Thanks for pointing it out... rmichael