I purchased two Aristo 100T coal hoppers, PRR, both had the same number. I managed to change a figure 5 into a figure 6 easily by using an old nibbed fountain pen dipped in white acrylic paint. A very fine black marker (the cars were black) tidied up one edge of the five.
I find that I have far more control over a fountain pen than a sable brush mainly it avoids hand shaking.
