You're not the first person to say this! I'm half inclined to use the Lowes shed as a starting point for my own design. But I do think I'd feel better if I could work as an "aprentice" next to an "old master". Someone at work is going to put me in touch with a guy who builds sheds for a living, and apparently he's competitive with the prices @ Lowes and HD. The Lowes shed comes with a "Handman Package" that I don't want but would end up paying for, anyway. The "workbenches" were laughably flimsy.
Getting a smooth, blemish-free finish with oil-based polyurethane is within your grasp if you follow the steps in this article. Oil-based polyurethane varnish brings out the wood’s natural beauty or wood grain. Our 4-step approach shows you how to apply the varnish successfully. A good-quality natural-bristle brush, a reasonably dust-free, well ventilated space and some patience are all you need. Learn how to apply polyurethane.
The last thing is to semi-permanently attach the bolts for the vises. Given the amount of work necessary to get to the bolt heads, once the top is joined, I had intended to tighten them up so they wouldn't spin, and lock them that way with blue Loctite. (That's the strongest non-permanent grade.) That didn't work. What I found was that the bottoms of the countersinks weren't quite flat, and when I tightened the nuts down that far, the ends of the bolts would be pulled far enough out of alignment that the vise bases would no longer fit. In order for the vises to fit over the bolts, I had to leave the nuts loose enough that the bolts had a bit of wiggle - which meant that they were almost loose enough for the bolts to spin. So I put Loctite on the nuts, to keep them from unscrewing, and filled the countersinks with Liquid Nails, in hopes of keeping the bolts from spinning. I considered using epoxy, or a metal-epoxy mix like JB Weld, but I didn't have enough of either on hand. It seems to be working for now, though the real test won't be until I have to take the vises off.