I have migrant issues. When I first started playing DF, I panicked with the first wave and abandoned...
...Micromanaging 7 dwarfs is very easy, but I'm having trouble adjusting to a less micromanagable fortress.
What advice can you give about career advising migrant dwarfs?...
Frankly, I don't think your problem is migrants, it's micromanaging. And I should know, because I do it too. Way.
The starting game is very different from the later game. At first it can be about micromanaging, but later it has to be about "policy" - you set groups or teams up within an industry, and let them work it out themselves. If it's not balanced, then you tweak the whole, but you don't worry if a few dwarfs show up as idle for a while - if for a few days, then something is out of balance.
There's no way that 7 dorfs - or even 20 - can run a fortress. A hole in the ground, sure. But if you want to move the next level, you have to get a machine going, and a machine works as a whole, not as individual parts. And if you want to take a swing at any sort of serious project, you need a serious machine.
Decide what industries you want to make work - metal, food, glass, cloth - and set it up in a serious way. Even for the secondary/support industries, by the time you're up toward 50 you can use dedicated specialists (or multi-specialists) - a furnace operator, a leatherworker, a butcher/tanner. Apprentice masons/mechanics who do the things your primary artisans shouldn't waste time doing. You need several legendary miners. And then there's the whole military process, which takes some management.
The support stuff should more or less take care of itself and be producing surplus - if not, add another apprentice or hauler or three to that category (food, stone, wood, whatever.) Like cjet said, there's always hauling - and if not, you aren't producing enough.
If you want to micromanage while this is going on, micromanage your project, or your one chosen main industry, or your military - only. And/or train up a chosen replacement for your leader should anything "untoward" befall them. Let the rest of the machine support that, and give you time to devote to just that one aspect, as you please.
There's a similar thread here, with more:
http://www.bay12games.com/forum/index.php?topic=34331.0