You can send FA packages containing troops directly to a country. 10% at a time every 20 hours As long as the country you are sending aid to isn't more than 50% larger than the country sending the goods
Other than that you would have to try to manipulate the market, and with a good like troops it would be difficult. I'm not too sure I know exactly what you want to do.
Pretty much this. In addition to the 10% rule, you also can't send FA to countries significantly larger than you (I forget the exact amount, 50% bigger? Someone will correct me if I'm wrong).
If you're just trying to build one country up, people have been taking steps to do that since the beginning, and there's meant to be some difficulty in just transferring all your goods to one country, so generally, you either have to do it at a slow and steady pace (like sending foreign aid packages of food each day, day after day, or you have to find other riskier ways of transferring through the market. Problem there is that everyone has access to the public market, so you have to be fairly clever in order to make that work.
Now, if all you need to do is send foreign aid to help out a country that's been attacked or that isn't doing as well, then you just need to find the foreign aid tab. If that's all it is, it's simple. It's just if you're trying to make one really big country by transferring, then it's a bit more complicated than just transferring everything to your best country.