Whatever has been working for you up until now will be fine, i think, if you got two months out of it. Just add the extra aeration and drainage in my opinion.
If you need new soil, then you can't really prepare it in time, if you need to compost it.
If this were the case in my own shoes, i'd probably just get some decent potting mix + some perlite. And some lava rock or gravel for drainage.
Lol and a bottle of premium charlie to use in a pinch.
Safer to also test the ph of the new soil when you pot up as well. That way you can correct things right there and then, if it's on the acidic side.
Shoot for about 6.5.