A word about external credibility
It's a whole thing
Think about the things that make you credible. Not the soft skills like “I’m a hard worker” and “I’m easy to get along with,” etc, but things that establish external credibility like titles, degrees, publication credits, awards and so on. Make a list of as many as you can think of.
Now, divide your list into two columns:
Column one is the stuff you’re really proud of and are proud to talk about to others. (i.e., “I worked my tail off and am really proud I earned that award!)
Column two is the stuff you’re proud of but that you sometimes feel self-conscious when discussing with others. (i.e., “I went to Oxford.” Which usually comes out like, “Oh, um, I went to school abroad, I guess.)
Now, sit with column two. Why do you feel self-conscious about those things? Sure, it might be because they are big, fancy things and people might think you’re bragging or completely full of shit, but I invite you to make a conscious shift. What if those things were more like keys than mic-drops? Keys that unlocked doors to other publications, to funding, to agents, to faculty positions, etc? After all, they are accurate things, and things you ostensibly worked your butt off to achieve, so practice ways to mention them neutrally, knowing you deserve to have accomplished fancy things, difficult things, and big things. You’re only stating facts, and facts that you deserve to have be true and known about you.