Putting my 2 cents in:
i. unless you are a flyweight carrying minimalist equipment, try to get 36h rims and hub. 32h wheels can work, but for that bit extra ruggedness and peace of mind, go for 36*. Just one unlucky bump can mean a broken spoke on a heavily laden bike -so I'd say go conservative. That's not to say you can't tour successfully on a 32h wheelset, just that I'd reduce my chances of problems.
ii. building a wheel for the first time for touring might not be the best idea. I strongly suggest you practice on some old wheels first, and then test them by riding on them. If you are short on time to perfect your wheel building technique, I'd say give that a miss.
iii. usually hand built wheels are better than machine built wheels. Why? Because proper handbuilt jobbies will have a better feel on each spoke for tension. Assuming a good quality rim, spokes and hub, this should mean a stronger wheel. One of the problems with knocking a wheel out of true or breaking a spoke is that you then put more stress on the other spokes (sort of a house of cards thing). Better not to knock your wheel out of true or break a spoke in the first place..... If you aren't mechanically inclined, I'd recommend having a trustworthy source check your machine built wheels before you go touring on them.
iv. have one, but haven't used it yet on any of the wheels I've built, but the fiberfix gets good reviews -might be worth considering getting one given how much weight and space it takes up.
*got to remember a good quality well built 28 spoke wheel is going to be stronger than any poor quality ill built 40 spoke wheel. However, all things equal, more spokes should mean a stronger wheel.