Fastest way to rebuild Feta

[Urs Liska]

Hi,

I actually did my first modifications to Feta (not intended for a 
general contribution but rather for a personal project).

If I use Janek's script to rebuild LilyPond it takes a mere 5-10 seconds 
to finish, which is quite good.
But is there a more straightforward (and faster) way to compile the font 
or even a given glyph individually to judge the results of the metafont 
modification? As long as I'm going through it by trial&error, even 5-10 
seconds sum up considerably ...

Best
Urs