Ben, colour matching can be difficult as many of our machines have spent years out in all weathers and colours fade. If you can find an area not exposed to the elements and sun, this will give best match. The Clifford Mk1 was a burgundy colour not orange.
Spray or brush really depends if you have equipment and skill to spray, aerosol cans can get expensive. If you opt for brushing ensure you get a paint intended for brushing and buy the best quality brush you can, be prepared to spend more time rubbing down than actually painting to achieve a good flat finish with no brush strokes. Ensure all paints you use are compatible.
Your paint supplier should be able to provide the correct primer and undercoat. If painting aluminium you will need to use an etch primer.
Here is a link to a photo of my SIMAR 35 which I brush painted, my first attempt at such a job.
