When I perform the focus procedure of the laser as per the manual, I found its a bit hard to see if it was focused properly while adjusting lens with the head fixed.
What has helped me considerably to find the focal point simply whilst performing the procedure is to place the focus tool as described, flat on the base but move the laser head up and down to find where the optimum focal point is.
Dot will go from big to small to big again as you move it down, obviously when its at its smallest is where the optimal focus is. I then position the head to where the dot is at its smallest and then check the height using the tool to see how far away I am.
I make an adjustment to the lens and repeat moving the head up and down to obtain the focal point.
I recheck the head height again using the focus tool as described in the manual, and keep repeating until I get the correct height and focus.
This has allowed me to get my focus correct very easily.