"uhh, lets see, that's uhh.."
This will usually get you the answer from the dealer AND give you time to recall the count, then add up your hand total. As Cobb says, if you trust what pops into your head, you'll find it's right. Just like seeing 5 cards and knowing the count immediately, many times you'll know your hand total immediately. At least you'll know if you busted, should stand or hit. You may have to total them after you've already given your signal just to be sure you get paid.