If you're planning to use a new barrel, or even a bourbon or whiskey barrel as a starting point, you should keep in mind the amount of time the spirit, apple brandy in this case, has contact with the barrel.
I once did a barrel aged IPA with my brother in law. He purchase an 8 gallon whiskey barrel (I don't recall where it was from). But we were concerned about how much flavor it would add because the aroma from the barrel wasn't very strong. We decided to get some bourbon and recharge it. We poured three bottles in and over a few days rotated it as you described.
When we decided it should be good to go, we dumped out the bourbon (put it back in the original bottles for drinking) and siphoned in the beer. We didn't have any instruction on what we were doing and it showed in the beer. There was no wood flavor, it tasted like we just dumped a bunch of bourbon in to the batch. I think part of our problem was we didn't rinse the barrel before adding the beer. So we had a beer that was flavored by bourbon rather than the saturated wood of the barrel.
I have also aged mead in a bourbon barrel. The first time was for 4.5 months, and the second time (same barrel) was for about 6 months. The meads turned out great, but after a thorough rinse of the barrel I couldn't smell any honey aroma. I don't think the mead left much of itself behind after that amount of time. I imagine brandy will behave differently, but it could take a long time to get the barrel saturated well.
Alternatively you might consider doing the barrel aging part first, and then blending some apple brandy in to the finished batch. If you start with a small sample of the batch and it doesn't work well, you should still have a good barrel aged stout