You guys apply and request to make a girl-boy Postcard shoot with us.
You do some reading and watching together to learn what we're seeking, and share some of your hobbies and sex practises.
We make a Shoot Plan with you with your ideas and our ideas, for each of several small scenes - maybe you head out for a nice meal, have a picnic at the beach, ride a bike in a park, go roller skating, or something like that. Then you come home and do something small and "domestic" together -  make a sandwich, hang out the washing to dry. Then, something a little sexual and playful - a massage, sexy charades, penis puppets. Then several sex acts (maybe, blowjob, tit-fucking, cunnilingus, penis-in-vagina A, penis in vagina B, orgasm, cuddle, clean up).
That's a bunch of examples, and we try to make each one quite different and interesting and with a lot of input from you.
We provide a lot of tips for the lighting and filming (your smartphone is probably fine), and we might send you some equipment (a cheapie smartphone tripod or similar), and tips on making a fun narrative.
When you're done shooting the plan, you upload the video files to us, we review them, and we might ask you for some "pickups" - extra shots for things that did not work out right in the original filming.
Then there's some paperwork, payment, and we're done!