I have used Testors model paint in the past on alternators, valve covers, "paint OK" on the fenders and underside of hood with exceptional results.
I use a Q-tip and roll the paint onto the letters/numbers of the rubber stamp and has worked out great.
I have also used the testors paint on tie rods, sway bars, spindles, transmission cases, etc,, with a small modelers brush, wherever a factory paint mark/slash needs duplicated.
*This information is my opinion and has worked well for me*