I can use the manager pretty easily- but getting all my work done and carrying on all the separate chains of thought is something of a problem for me- I can do about three things at a time... sort of. Deathtraps are basic, garden variety traps... oh. That's not my problem, it's getting the trap components.
Well, if you want to build a better deathtrap,
and the FBs will beat a path to your door what you really need is a basic understanding of mechanics. There are really great deathtraps just floating around the wiki or forums that you can copy and modify to your heart's content, so long as you understand the basics of how mechanisms and such work.
Again, I recommend just flat building a fortress to test things out so that you can grow more accustomed to what you're doing, and understand the principles the more complex things are built upon. The wiki has great examples of basic mechanics.
To give an example, I'm currently using minecarts to stockpile wood from the surface in an underground segment of fort. This means falling logs that might hurt my carpenters if they happen to be picking up some wood at the wrong moment. So, I want a hatch over the last tile before the stockpile, itself. The problem is, however, that a pressure plate one tile away from the stockpile will only send an "open" signal to a hatch when a dwarf stands upon it, not a "close" signal. I need a signal inverter, or, as it's called in boolean logic, a not gate.
The Minecart Not Gate is an easy-to build feature that produces an inversion of a basic signal. Hence, when my dwarves step on a pressure plate, a hatch overhead closes, preventing falling debris from hitting them, and it opens again ~120 ticks after they have left the stockpile.
As for trying to get trap components and industry working, I generally don't worry too much about it, myself. I just order things when I need them, and then check in on them occasionally and randomly. In general, my play strategy is to spend 2 hours designating a bajillion things, then let it run for a while. (How long depending on current FPS - I'll let real FPS crashers running at 2 FPS run overnight, and check in on them once a day to give new orders.)