Cover EVERYTHING up before you start!
To be honest mate you're gonna struggle unless he's a good 'un and can get right back into the swing of things. It's a bit difficult to describe how to do it, you really need to be shown on site. You're gonna need a bit of a practice swing first - somewhere that you can scrape off once you're done.
I was told to hold your dash trowel like you're shaking someones hand, nice firm grip. Stand at 90 degrees to the wall and get ready to get sh!t up!
Some blokes lift the roughcast/wetdash/harling straight out of the bucket, but I prefer to take it off my handboard for a more even finish. Each to their own. I'll assume that you can dry dash so the arm action is quite similar to that and as each trowelful leaves the trowel the leading edge of your trowel should be parrallel to the wall.Next you need to LISTEN to it as it hits the wall. If you hear a SLAP you've done alright, if you hear a whooshing kind of noise you're probably not covering the wall sufficiently and will leave loads of 'blacks' which will look shoit when you're finished. Your back will ache, your arms will ache, your shoulders will ache and you will NEVER WANT TO DO IT AGAIN. Go home and have a fkin good wash, you'll need it:RpS_thumbup: