It's mainly ALA which you need to wait on using. The problem is that ALA removes mercury from your brain, but it can also carry it into your brain as well. After filling removal, there will be a lot of mercury floating around from removal. ALA can take that stuff and deposit it in your brain. That's why you wait 4 months before using it. The bad effects of using it too soon may not be felt immediately. You may only notice over the long run.
The best thing to do is use a different chelator, like DMSA, now to reduce the amount of Hg in your body as a whole before you begin using ALA to remove it from your brain. That way there's less Hg in your body which might be carried into your brain.