Enameling on brass is the least expensive metal to enamel on but it is also the least friendly.
Enameling is growing again in popularity in the US, and many look to brass because of is low cost.
Thompson’s Enamel sell what is called guided metal which is brass with 5% zinc and 95% copper, = Brass. This is a brass you can enamel on. Caution need to be used to plan you execution of the enameling plan as you only have 2-3 firings before the enamels like to pop off.
One reason you will see limited colors and opaques used on brass.