For 3 doors it's not worth it. I'd get a quote for the job, then compare it against the cost of a decent capacity compressor, spray gun, air line, da sander, sand paper, panel wipe, thinners, primer, top coat, masking tape, and a face mask. Aerosol cans plus all consumables listed above are the only viable option, even then adding your time into this it's a close run thing between paying someone to do the job.