I think the best way is to simply eat a big dose all at once. Redosing on mushrooms make the whole experience even more filled with anxiety then normal. For instance on 5 grams of mushrooms I might not peak till the 3rd or 4th hour if I keep toking, and then still have a nice plateau for another 4 or 5 hours. If I only eat 1.5-2 grams I'll be peaking between hours 2-3, then be pretty much down in another 2-3 hours. If I eat say 3 grams then another 2 grams at 2 hours into the experience, then yes, it will have a longer peak maybe stretching to the 5 hour mark, but for the first 4 hours I will have been dealing with the rather uncomfortable mushroom come up. Best just to let it hit u like a ton of bricks all at once I think, then to deal with that. If ur looking to milk the experience just use herb, it never fails to recrack my head open when I seem to be coming down.
Its the same deal with redosing at 6 hours. Think about it, if you took a new dose at 6 hours you'd already be coming down a bit, and by the time 2 hours had passed and your current dose had sent you back off in space, your first dose would be mostly gone and would not really compliment the second dose. plus by then tolerance will be in effect