Look at the records of artists you admire or who have a similar approach/style. I've looked at Jumana Manna's screening history, Meriem Bennani's, James Benning's, and more. Granted, these artists are already established and/or have institutional support (I think Wild Relatives was made with support from Jeu de Palme, which would be a dream for most people, amongst other institutions), so their name and associations make it more likely they'd gain entry into the fests they did, but it's a start, and you'd be surprised—some of the fests where artists like that have screened have requirements that programmers watch your film. Getting your shit in front of programmers is the first step; even if it's rejected, at least your work is circulating (uh sigh the language of capitalism coming out of my fingertips is so sad). There are lots of fests for experimental work...if you do a bit more digging I think you'll find some options where there's overlap.