Depends on the weather but three or four or five hours is not unusual.
Painting steel house siding.
Begin by thoroughly cleaning your siding of all loose dirt chalk and other contaminants.
The first step includes cleaning.
But i would use the oil based rust oleum primer which by the way takes forever to dry.
Step 1 clean the steel siding.
When this happens the metal is exposed to the elements and will start to eventually rust.
That is how you can get the paint to adhere to steel siding.
This is followed by fading and thinning of the color.
The first sign that this is beginning to happen is a loss of the glossy look that new siding has.
It also helps to peel away the previous paint on the steel siding leaving it neat and clean.
Cleaning of the surface can be done by hand washing with warm soapy water or with the use of a high pressure washer 2500 psi minimum.
Then apply the primer to the metal siding in even strokes.
Do this as soon as any spots start to show the steel underneath or do it a little sooner if you are trying to sell your house.
Since any of this is clearly bad for your metal siding it is vital that you re paint your metal siding.
For steel use a latex bonding primer instead of a regular metal paint primer.
Start at the top of the wall and across the length of the metal siding.
As with all exterior painting projects proper surface preparation is the key to restoring your metal siding.
Trigger the sprayer to begin the paint flow and use a back and forth motion to cover the length of the panel with an even coat of paint.
Wash the steel siding with trisodium phosphate tsp and use a pressure washer to rinse thoroughly.
And then i would use the rust oleum top coat.
Paint the steel siding panels using the sprayer.