If you're serious about it and want a budget job, strip the bikes, rub down with wire wool to remove rust and take the sheen off the old paint, then wash the whole frame in hot soapy water and allow to dry before painting with a metal primer in a similar shade to the final coat. Rub down gently with some fine paper then wash again or at least go over it with a damp cloth.
If the frames are aluminium you ought to apply an etch primer to bare metal if you want to do a good job. This is the yellowy-green colour you see on aircraft before they get their livery
There are all kinds of fancy hand-applying paints for vehicles, for example alkyd resin paints but they are expensive. Believe it or not Dulux Once is an excellent paint with good coverage and a super shine, easily available in small pots. I used to paint my Land Rover wheels with it and it lasted well. Watch out for dribbles though. I expect you could achieve some rather cool pastel colour effects with this. Alternatively go for a matt, which is very trendy at the moment.
You'll need to arrange somewhere dust free where you can hang the frames up to dry for 48 hours. Professional painters will actually wet the floor of the paint shop to hold dust down.
Alkyd resin paints:
http://www.hmgpaint.com/welcome/
Hand painting a vehicle:
http://www.lrfaq.org/Series/Other.paint.top.html
Some cool pastels here:
http://www.paintman.co.uk/paint-colour-chart-range-rover.html
THE definitive website on hand painting vehicles:
http://www.stephen.hull.btinternet.co.uk/