I have never done patches, i have pulled entire machines down to do it....
Ken did his a few years back with a sand blaster on the rusty patches then filled and painted them up, came out pretty well!
I have used equipment enamel twice and two pack once. Enamel is great as its easy to clean and mix but i really don't like the finish. If the weather isn't just rite you get dusty areas from where the paint dries a little too fast. I have also found that rust can come through it pretty quickly even when the area was sand blasted first.
Two pack gives an awesome shine and tough finish, i painted my 743 3 or so years ago and there are no signs of rust. The paint is a pain as you need to mix enough for the job and any left over is wasted. It STINKS you need a respirator as its not good for your health. The over spray gets on everything as its slower to dry. Don't apply it too fast or it will run, give it time to flash between light coats. The surfaces must be oil and wax free, any oil and it will make what some call fish eggs, little spots where the paint will not cling. Enamel seems to be a little more forgiving on this.
I just used off the shelf white and black for mine. I got the orange for the door and rims mixed and used enamel as these don't really matter as much.
Personally for a long lasting finish i would look at two pack but be prepared for some horrid smells and mess from over spray. The end results are totally worth the effort though.
I'm sure others will have different views.