just getting back in to drawing/painting after a few years and i'm trying to move from small to large... paper to canvas but finding it frustrating. Reasons: one - that acrylics mix really differently to watercolour and ink and two - i really like using a pencil/fine line pen to confident lines which is harder with a brush (esp on canvas). any suggestions? i've seen artists like anthony lister killing it with spray cans but i'm not quite ready for that.
Sketch lightly with pencil first, then paint over. Seen a few artists do this and seems to work well (and something I'd like to try myself one day). You could even start combining both pencil work and acrylic to have a kind of mixed media type outcome.
I'm new to the painting world too, and I've been through the same pain as you.
Don't stress about mixing. Just make sure you have some jars around the place to mix into, so you can seal them up and revisit the colour at a later date. I've found that baby food jars from all my nieces and nephews make for a great system. Same as those little plastic containers sauce comes in from a fish & chip shop.
The brush is a tricky one, but spray paint is even trickier (unless you have a super loose style like Lister, which it doesn't sound like you do)
The tough truth, just learn how to use it. You'll be amazing how quickly you get better at using one. It takes time, but the hardest part is learning how to load the brush with enough paint to keep a line going. You've also got to keep in mind that the distance from the canvas (or how hard you're pushing down on the brush) is what dictates line thickness. It sounds really obvious, but it's something that I always seem to remember right after I've fucked up a particular line I'm working on.
The great thing with acrylics is that if you make a mistake, just wait a few minutes and go back over the mistake with the surrounding colour.
I always pencil in my paintings, and as long as you put enough acrylic back over the top of it, the lines will disappear. In fact, I find the lines I put down often end up only as a guide for my colours, then the outline I sort of make up as I go along.