Hi Helen,
I am going to use There Are The Guns, although They Died For Glory would work well with some mechanics introduced from Peter Pigs Patrols InThe Sudan..might sound a bit of a mix up but I could not find any rule set that gave me ideally what I was after.
My Units are based on stands of two figs (2-7 stands per unit) plus Command or NCO stand thereby the unit can become either a battalion or smaller company style unit. bases are 40mm by 30mm for Infantry 40mm Rounds for Brigade stands, 60mmby 60mm for Artillery with crew mounted as individuals
Cavalry will be single casting on 40mm frontage by depth required.
Divisional or Corps stand will be 80mm round or square.
If I was starting from scratch again then I would recommend for large battles any good set of Franco Prussian rules, for smaller skirmish actions or RPG any skirmish set you feel comfortable with.
Wht one has to keep in mind this war was not only fought in Bulgaria but also was fought through the arid regions of Armenia