Macros doesn't matter to gain muscle or lose weight and is a hard to kill myth.
And saying eat "x of what you normally eat" is bit odd. So if i eat my protein requirements already, I should increase it by 3 times?
All you need to grow muscle in terms of diet is about 1.6-2grams of protein per kilo of LEAN muscle. So weigh yourself, remove the bodyfat and voila.
There's rarely, if ever, a need to eat 300grams of protein per day. That would mean you're 150 kilos LEAN MUSCLE machine, which, not many are lol.
And you'll need even less to just maintain.