Hey there, I really know what you mean about trying to get your sewjo going again .... I have regular bouts of "I am hopeless, and these machines are useless" episodes, although they are becoming less as I learn more.
I don't know of any tutorials, but I can tell you about my own experience. I made a linen dress ...... the fabric was stunning, but the pattern was a style I don't normally wear. Sure enough, I made the mistake of cutting my fashion fabric before doing a muslin .... and of course the darn thing didn't fit. While my first instinct was to turf the thing, I asked for some advice for options here, and then took the plunge. I inserted panels in the side to give me more hip/tummy room, and instead of trying to hide the alteration, I piped the edged with a contrast, and made a feature out of the alteration. My piping wasn't standard by any stretch. I used 2.5cm bias binding, ironed it flat in half, then just sandwiched it between the seams. With a 1cm seam, that meant that .5cm of piping poked out of the seam all the way along. I seriously doubt its how the professionals do it .... but it worked for my dress. And since I have actually worn the dress three times since I completed it, it was obviously a good enough solution.
If you would like to see my dress and its evolution ..... its here.
Sewing Discussion at Stitcher's Guild Sewing Forum » Types of Sewing » Individual Projects, Projects in Progress, and UFOs » Linen dress - wearable now
Best of luck with your jackets.