I repainted my commuter 4 years ago and it has survived outdoor living over winter.
Assuming the bike is steel, (if it is Al then dont do it)
Take the old paint off by sanding. You may want to leave the old primer if it is sound. (it is the light coat under the colour.
Wash and clean and dry the frame.
Put bolts into the threads.
Smear some grease onto the BB threads if you sont want to chase out the paint later.
Suspend by a wire through headtube /BB or dropouts.

Apply primer, then topcoat.
Aim for a speckle effect, rather than a complete coating in one go. Too much paint will run and drip. Several speckle coats will make a complete coat
When you are reassembling the bike, put aname and address label on the steerer tube, and in the bottom bracket.

Think about rustproofing inside the tubes. I use a good spraying of WD-40 into every tube I can.