I haven't seen a ton of fics that drill down into just Kankuro and Kiba's friendship, which is a shame because their dynamic has so much potential. A lot of the ones tagged for them are really about the bigger Akatsuki or war arcs, or they're part of a larger ensemble piece where their interaction is just a side note.
What I look for is when a writer actually gets their specific vibe right—Kiba's loud, instinct-driven loyalty clashing with Kankuro's more cynical, strategic puppeteer persona. They're both fiercely protective but express it in totally opposite ways. There's this one old fic, 'Of Dogs and Crows,' that did a decent job post-war, having them bond over being the 'forgotten' older brothers in their respective trios, dealing with the fallout while their siblings got all the glory. It wasn't a romance, just a grudging respect that turned into a solid alliance.
Most of the time you have to sift through the KibaHina or ShikaTema stories to find little moments where these two butt heads or have a drink together. It feels like a niche within a niche.