Barry, I'm basically going to say what has already been said with a few exceptions. The first being, a welt foot is personal preference. I hate them. In 25 years of upholstery I have never used one other than to try one out for a few days. I hated it the first time I tried to sew a tight corner. I can get the welt tighter with a ground down walking foot and don't ever have to change the foot, but I also run the risk of running over the welt much easier, but like anything else practice helps. Every upholsterer at one time or another has run over the welt and ruined all or part of their project. However, since you've stated that you are a beginner it's probably not a bad idea to use a welt foot until you get a feel for it. I agree with Dan on Taylor's book, it tends to very non-descriptive. Even when you know what they are doing the descriptions don't make much sense. The book is good for pictures and ideas, but lacking in the description. Most books show a nice finished project but neglect to tell the reader the small things that make a huge difference in how the project turns out. As for adjusting your timing....DON'T.
If you think you have problems now, just wait until your machine starts skipping stitches or knocking itself out of time because the timing is out of whack. Timing is not your problem. Thread problems are nothing compared to timing dilemmas. From my experience, shredding thread comes from a burr on the tip of the needle, crappy weak thread, a burr on the thread hook, or a groove where the thread has worn on the thread tensioner...in that order. I'm glad you're attempting to sew your project yourself, hang in there, you'll figure it out. You got a good deal on your machine and as long as you keep it oiled it will out live us all. If you need help with your projects, just ask. This is off topic, but you mentioned being a gunsmith, I thought your government stripped the citizens of their right to own guns.?. Take care,