not-close-to-straight:

Try writing them in a VERY au fic or short story.  

Like when I was getting to know the Spideypool characters, I wrote Bad Ideas because adding the ABO element forced me to round out Peter/Wade in a way that maybe wouldn’t happen in a fic otherwise because ABO includes all the emotions/hormones/etc etc so every single moment was 100x more intense. 

ie: The scene where Wade is triggered and slides towards a mental break. In a regular fic, Peter’s part is basically offering sex to distract Wade and then getting upset and leaving when Wade snaps at him. BUT since it’s ABO, it’s all about the way Peter is using his Omega side to calm Wade down, offering submission because he knows it’s good for the Alpha, Wade pushing him away because he knows he’s very close to breaking and doesn’t want to hurt Peter. 

Or as I was getting used to writing Stuckony, I did it in TEASE where Tony is basically a lacy panty wearing cocktease and Bucky and Steve are hopeless and helpless and Natasha was super friendly and not at all scary. 

This way Tony didn’t have any angst because of PTSD, and there was no “oh no the Winter Soldier” dynamics so I could work on how I wrote them laughing or the sexy times or even just working on Tony and Natasha’s friendship. 

Writing something that lets you ignore the “canon” view of the character and work on sort of ridiculous HC’s about them will help you round out the character in your longer fics. 

like you’ll notice in all of my Spideypool fics, they sleep with Peter curled up ontop of Wade. literally on top of him. Straddling his waist, face in his neck, in every single on of my fics. I thought it would be cute in Bad Ideas, and it made it’s way into everything else, and now it’s a way for Spideypool to show complete trust in each other because it’s sort of a vulnerable position for both of them to be in. 

“Sure thing, sweet thing” came from Letter’s to Bucky which was VERY au but let me explore the winteriron dynamics without all the angst from the MCU, and it’s completely affected how I write Bucky because it’s such a romantic thing to say which makes me write him as if he’s a hopeless romantic beneath all that Growly Goodness. 

Anyway, I’m rambling sort of, but the point it– when you want to work on rounding out a character, try writing them in an AU outside of any of their normal angst. Without that pressure to keep them “in character” you can work on all the different nuances and end up with really well developed characters

This works really well in rp as well, since it’s the same concept. Most of my muses I picked up in au rp groups and they stuck around from there.