The "one-shot" brand paint is used by sign painters. Look for it at stores that supply the trade. Model enamel will not work as by the time you thin it to flow, it will not cover and does not level out well.
You need a "sword" or "Dagger" brush (try auto paint supply stores, they are also used for touch-up). The paint must be thinned with some linseed
oil to allow it to flow and so the brush can be moved over the surface without "dragging". The brush is stroked back and forth over the paint/
oil mix on a stiff card to "load" the brush. To make the line start at one end and with the brush at about 45 degrees meet the surface. Pressure will allow you to control the width of the line.
I am not a striper but know some guys who are. I have tried it and I can control the line width but have no "eye" for form and I can't run a line straight and even. Eastwood sells a pinstriping book and all of the supplies, check their website...and don't forget the hack's guidebook.......Google!!!
A lot of practice and you will "get it"