Custom Button for all products - 485 prodcuts

Hi, is there a faster way to  Custom Button for all products so the flow goes like this

Add to cart - product page opens / next button says (buy now) can i apply to all the products using CSS in the advanced settings header injection or?

do i have to manually change every product to have an enabled custom button then type on every product in the product settings

buy now? 

its taking so long! there must be a more efficient way to apply this?

I can only speak to the text of the button, not the rest.

CSS alone won't get the job done.

Please see the following.

Let us know how it goes.