Good plan, I'd really suggest getting your own liquid test kits but if you have to wait just make sure you get the numbers from them. There isn't anything wrong with dosing buffers but you shouldn't be dosing anything you don't have a test kit for. It is too easy to overdose. And in my opinion, you don't need to dose to get your rock covered in coraline. You simply need time. Do you have a photo you could share of your tank? Although we are strangers here it might help to get some advice from other hobbyists that have gone through what you have. Personally I found it very helpful and discovered that some of what was being said to me at local stores was fine..but some wasn't. It was a blessing to know a little to sort out what was nonsense being fed to me.
