Someone in the comments asked about projectors. Was I pro or con on projectors? I would have to say I'm "agin em" Here's why.......
They won't do what people think they will. No one brings them up because they want to enlarge their sketches. The purpose of a projector is to copy photographs. But that won't make a painting. If it did, everyone could paint and of course few can. If the idea is to make a salable thingy, the projector might do it. As I have said before, every gallery I am in has someone who just copies photos literally, and they tend to sell pretty well. So you can use a projector to make a close copy of a photograph. But that's not a painting, its still only a photograph, but now it's made out of paint.
So it doesn't matter how you copy a photograph, whether you use a grid to square it up, or squint at it pinned to the corner of your canvas, its still the same thing. Copying photos is just busy work, it's drudgery and without creativity. Copying photos is the most boring thing imaginable.
I see so many paintings made this way in the magazines and they aren't compelling or interesting. I just turn the page. Anybody with the patience can do it, and a roomful of patient airheads with the same photo will all make the same painting. There are collectors who exclaim "it looks just like a picture and imagine the painting is "perfect" and for them it is. But it contains no art. Art comes from decision making, things like handling and design.
There is another problem with projectors. They give an absolute outline of a literal scene in front of you, or an object, but they don't give the information to describe the form within that object. Form is a construct that cannot necessarily be observed, it must be installed to some extent. A very practiced artist can do it, but a learning artist never will. Nor will they learn drawing by trying to copy photos. You have to actually learn to draw to have command over what you represent rather than being chained to the most cursory and literal presentation that is styless. So many people want a short cut, an easy way to be a painter. You simply have to be able to draw. A projector might seem like it will enable you to do that, but it won't.
So the answer is not projectors yes or no but, projectors, what use are they to an artist?