Classic/Antique Car Repair: SBC valve seals, small block chevy, spring tool

Question
I am installing a cam in small block chevy.  Changing springs,locks,retainers, and seals.  Using compressed air to hold up valves while changing componets. Using spring tool that installs on the bottom of spring and turn the top wheel to compress spring.  Having trouble with keeping the o-ring seals in place while compressing the spring.  The retainer is pushing seal out of position when compressed just enough to get the locks on.  The valve is completely closed.  I know these types of changes with the heads on can be challenging but I must be doing something wrong or this is not the best type of spring tool??
Thank you

Answer
I never have seen a tool like that, the air tool is ok but do not un plug it as you will have to take the head off. I would go to a tool rental place and get the small bar that you put on the stud than put the bolt on it and than all you do is press down on the spring  and it gives you a lot of leverage. and put a drop of grese on the o ring to hold it. sorry for taking so long had some trouble at home