A good chunk of my sewing skills are self taught. That means a good chunk of my sewing skills are made up things that work for me.
I start by serging the edge of the sleeve or pant leg needing to be hemmed.
I double the size of the hem I want and draw a line. For a half inch hem, I draw a line with disappearing ink 1 inch from the edge.
I iron the edge up to that line and sew. Instant hem before assembling the sleeve or leg!
Of course, this doesn't work if the top or pants are already sewn together, but it's my shortcut when I'm starting from scratch!