@@ applies the previously applied macro, so after applying the macro (including the move to next line, but see below too) you can you just hold down @ and quickly go through as many lines as you need. If you overshoot, you can just press u a few times.

Another tip: when you forget to add the move to next line to your macro, you don't have to start over. You can append to a macro, just use the upper-case register name instead. So to append a down and move to beginning of line to macro 'a', you'd type qAj0