I've always used a cup of ACF50 and a small 1/4" brush and gone front to back over the bike painting every fastener and spoke. I then dip a clean rag in the cup and wipe the ACF50 over larger metal surfaces such as the forks, bars etc. I would give the engine area a bit of a spray, but the spray was never much good.

This year though I treated myself to a Bosch paint sprayer (the wife thinks I got it to do the fence panels in the spring!) The sprayer is awesome. I still paint the fasteners by hand first, but I then cover the wheels with a sheet and spray all over the rest of the bike and it leaves a really nice light mist. Now my mates bring their bikes to me for winter prepping as well as cleaning!