I've heard good things about crushed coral too...
used the same way as dolomite.
I think maybe dolomite only works with EXTREMELY soft acidic water-
mine is around 6.5 with a GH and KH of around 1-3... the dolomite doesn't do anything for me.
If you want to measure your DH/KH you can always triple or quadruple the amount of water-
(instead of 5ml, use 20ml) and divide the number of drops for the color change by 4.)
My GH at one point was unreadable, until I did that and found out my GH was .75.
Since then I think the dolomite did increase it a point, but the PH is the same.