For the smaller kits that are around 3wks old, you will need another hand to use an extra finger or two to gently push down, wiggle and pop out the sex organ. Does will only show a triangle, it can look like a stuck willy. A buck can also look like a doe if you aren't able to fully pop out the tube. Honestly, just wait another week and they will emerge far easier and less guessing. It's also stressful for the kits, they don't like you messing with their sensitive little parts and it's easy to accidentally pinch or scratch them.
Bucks, from 2.5 weeks to 5 months old.
Does, from 1 day old to 6 months old.