For example, stack of 3 1:12 friction (or timing belt) reductors will give you overall reduction of 1:1728. With 200 steps motor, it is more than enough for 300mm lens.
My belt-modified EQ6 (as well as yours) has 1:900 reduction (180*5).. and 400steps/rev motor..
BTW, have a look at my mount for wides (including 300mm).
http://www.iceinspace.com.au/forum/s...&highlight=eq3