I was down at ATPs at Craig Field. Not including the private, which I did in high school, about 3 months flying at least every other day, if not every day, with a week of just studying in between a couple times. I had 100 or so hours before I took the private multi, though I hadn't flown in over a year and only had 8 flt hours to prepare for it. That's when sims can really come in handy.
During instrument I flew maybe 3 hours a day, almost every day, along with some time in a simulator. During the time building, which was all done on instrument flight plans, I believe I flew about 30 hours a week for maybe 2 and a half weeks. 95% of the multi time I have, sent you a PM earlier, is flying instruments.
It was about 120 hours ( on top of the 100 or so before the private multi ) in 3 months, not that bad, and can be done if you don't have any obligations. There was no rush for me, just plentyof time to knock out some ratings.
The school I went to, ATP has a good program, nice planes, but it has a few flaws, and they just jacked up the price another $5k. They offer way more than anyone needs at this point, and really ought to offer something with not as many certificates, or a commercial program, and maybe just a CFI, not the entire CFI/CFII/MEI, or an a la cart option. I have no idea why they offer their citation jet ride. Though you are doing something completely different with your cousin, and that's way better than most of us can do.