Your mentor is a sweet dear old soul. Thank her and move on.
1.) I use a 40 YO Bernina. Goodness sakes, you are sewing in a straight line! a 1/4 seam! There are people on this board who use treadle powered sewing machines. My local quilt dealer rolls his eyes anytime I come in. He knows I could afford a new machine. I know I could afford a new machine. But why? Your Brother sounds just fine.
2.) I feel bad for all the people whoever get one of my quilts. I break every rule. I measure along the side, cut enough fabric and join it together with a couple of inches left over, I attach the border, then trim it on a long table with a 24 inch ruler running down the existing end cutting it as if it were another addon piece of top. Which it is. So what have I done wrong here? Used fabric that was not cut parallel to the selvage. Pieced it, usually with straight edges instead of 45 degree angles, didn't measure the center of the quilt (the border ain't on the center, now is it?). Didn't miter my ends.
When I am finished all four borders, I might put four more on, the same way. In the end, I measure the quilt (to make binding). OH no! this edge is 3/4 of an inch longer than it's opposite! Too bad. I have yet to find a single person who gave back my quilt because it wasn't square.
Now, here is the only rule of thumb I follow. If you can't see the error at 55MPH as you drive by with the quilt hanging on a clothesline, the error doesn't exist. Because NO ONE else will see it. Remember, this is cloth. It is a breathing beautiful extension of your own creativity, bound only by the love you give it as you make this artwork that will be cherished and loved. tim in san jose