Seems to be pretty weather dependent for me whether i find them talking early or not. Hot and dry? pretty quiet.... but: an hour or two before daylight i can still find bugling bulls: they just tend to get to bed before sunlight to stay cool i assume.
Same problem as you: units i hunt arent great for glassing in, there's a few spots, and you can often see elk from those view points, moving across small openings across the valley, which is fun but you still gotta hunt them in the deep timber anyway.
Back to the above, i try and move quietly before dawn, use location bugles, and see if i can pinpoint where they are while its still dark, then if they are way off, make my way towards them in the dark, if they are nearby im gonna sit tight.
When it's hunting hours i'll see if i can get another response with a bugle: if i do, ill go into a sequence and see if he's game and wants to come in and investigate, if that fails, i'll very slowly start to stalk around towards where i heard the bugle coming from, making very faint cow calls if i feel like im making too much noise. Thing is here: move slow: whats the rush? you know there is a bull around, he's likely bedded down, you just gotta keep the wind right and not blow him out.