Painting both sides of a shelf?

[cuboid]

If u need to paint both sides of a shelf what's the best way to paint other side without pressing on already painted side?

Also, I painted the undercoat with a brushigh but want to spray the 2nd coat with from cans in picture. Good idea and what's best way to do this?

 

[footprints]

Screw something like a couple of vine eyes in the back edge of the shelf that is hidden and clamp upright in a workmate perhaps?

 

[chappers]

wait for it to dry is the normal way.

 

[cuboid]

The undercoat the lady gave me is from b and q but the spray paint is for cars. Is this a good idea? That's what the lady gave me which someone else used.