I can't do haircuts alone, I need help. I cut Ds2 first and DH or dd2 take him to the shower, he's in a diaper and off somewhere away from the hair (I cut in the master bathroom) when DS1 is done and I pop him in the shower and rinse him (he hates showering, this is a loud and ugly situation), wrap him and hand him underwear and then hop in the shower myself. While I'm getting cleaned up DH sweeps up the hair mess. It's a whole thing and if the boys didn't have such unique hair texture (it is an incredibly thick brillo pad texture and mats horribly like >that< ) I wouldn't even bother.
The girls I give a trim once a year or by request at a completely different time and usually outdoors so the birds can have the clippings.
ETA: I use and apron for me and for them, that really does help. I also keep a little pastry brush (looks like a medium size paint brush, I'm not sure where it came from but it's definitely kitchen related
I'm sure they sell actual hair/skind brushes for this at a beauty supply store.) and I sweep DS1's face and neck briskly every minute or two (he HATES the feel of hair on his face and neck). I sing "Painting the roses red" (from Alice in Wonderland) loudly while I sweep DS1, he's 4 and finds it hilarious and it helps make the whole project less agonizing for us both.