acid rests add a lot of time to your brew, it's quicker to add lactic, phosphoric or calcium chloride to the mash to lower your pH. You can also add the buffer 5.2 stuff to take the guessing work out of your brew.
I wouldnt use an acid rest to correct the Ph only to help create ferulic acid that a hefe yeast can turn into a clove like phenol. add some gypsum, lactic acid, phosphoric acid, calcium chloride or Ph 5.2 buffer.
It's a blend of phosphorous based acids and bases that will buffer the pH to around 5.2. If the pH is higher, the acids will lower it and if too low, the bases raise it.
It is a handy little product, but with a little work on your part, you can make salt additions to your water to achieve the same result.