I was looking for this too. I have my own workaround... I use a little Mac app called PopClip (it's the greatest) It does a ton of stuff beyond what I describe here.
with Popclip, I select the text I want and copy it. Theres an extension you can get for it at their website which pastes what you've copied but removes any formatting. I paste it into something that has the formatting I already want (made once) and whatever I paste assumes the new formatting of what you're pasting it into. Not perfect, but fairly painless.
Just in case I'm not clear, here it is again in slow motion...
1 - have something created in the format that you want - Font / weight / size etc.
2 - copy the text that you need to change
3 - paste that text into the the text from step one. You have to use the extension that strips out formatting as you paste, otherwise it will keep that formatting as you paste it down. This is an extension that you add from their website (it's free, the app isn't but ridiculously reasonable).
I'd put a link in here for the software, not sure if it's against the rules. Google will do it for you - popclip app should do it!
Hope this helps