Chris Green/Flumpmaster did his F18 sails using the same techniques as the Euro teams, maybe he can share some of his experiences.
I painted a Hobie STX main in 2009 in advance of the Tybee 500 with a Texas Flag design. I used Martin Senour Auto paint with a Urethane flex additive used on Car Bumpers. The paint has held up very well on the sail cloth - no flaking off at all - despite over 1000 miles of hard sailing between the Tybee, GT300 and other races.
I applied the paint using Preval spray cans - because I did not have an HVLP rig at that time. I used approx 15 preval power units and 4-5 glass bowls. I wore a tyvek suit, Nitrile gloves taped up and an air fed mask because of the toxicity of 2 pack paint while it is curing. I started out with a brand new sail fresh out the wrapper.
I prepped, masked, sprayed, each section of the design at a time - 3 per side, 6 total. The star was a vinyl graphic - in 2 pieces because of it's size vs. my friends vinyl plotters max width.
1. Large smooth floor area, well dusted room. I used a large canvas floor cloth over my garage floor to lay the sail on.
2. Wash sail with warm soapy water and a sponge to remove any dirt/dust. Dry off (I use a hair drier)
3. Key sail with a scotch brite pad - enough to remove the high gloss when looking at the reflection of a flash light. Don't scrub the stitching.
4. Wipe sail with Acetone to remove dust and any residue not removed by the soapy water.
5. Mask area of sail to spray. I used 3M Blue tape.
4. Spray adhesion promoter - this is almost like contact adhesive. It is part of the paint system and is used to promote adhesion to plastic components.
5. Mix paint, catalyst, thinner per manufacturer - and flex additive. I used twice as much as recommended - not sure if this was necessary but it worked fine on a test section of cloth I did during my R&D.
6. Spray a coat, No tack coat necessary (because of the adhesion promoter). Let the solvent flash and re-coat - about 10-15 mins.
7. Leave a day before removing masking and moving on to the next area. It took me 6 nights of work (actually 7 because I changed my mind on the size of the blue panel when I started the job).
We used the sail within 4 days of painting it. I did have the advantage of Texas heat to aid curing.
The result is stunning - the colors 'pop' a lot more than a vinyl graphic stuck to a sail. If I do one again I will experiment using my HVLP turbine sprayer - as the prevals don't have much capacity and quite a narrow fan.