The MIR is different for different companies, depends on who handles the MIR for the company u are purchasing the product of.
In any case, what u have to do is snailmail a form to them, and they send u back a cheque in few months, but it's not as good as it looks on paper, otherwise they would just sell he thing at that price if they wanted to. They check a thousand things, and don't give MIR for insane reasons. Order stuff that has no MIR, or if it's a good deal upfront, forget the MIR while ordering, and then still if there are things in ur card with MIR, u can tell him to give it a shot.
In my opinion, just order the stuff before he is leaving, stay put for a while. I've made mistakes of hurrying up and ordering stuff beforehand, and ended up having to sell stuff at price lower than I got. If he is ordering stuff for you, I mean he has the cash, and u are gonna pay him wen he comes here, it will be better, If u are ordering from here, and getting it shipped to him, u better have Paypal, and be ready to pay more.
I have also purchased used Items in US and got them shipped to my friends there, and actually, I find that more easier and hassle-free. In any case, I have always ended up paying a lot more than the prices that seem there, u pay shipping, u pay more because all stores don't take international Credit card, those that take, usually don't offer good prices. I even had to bear the 5.4% fee paypal charges on CC transactions in past.