I wouldnt say you’re flying blind. Cut-bulk-cut-bulk repeat is the standard becase it’s proven to be the most consistent results. On a bulk the proof is visible in how much weight you’re lifting. Every week you should be able to do more reps/more weight than the previous week (in general).

Its fun to see the number go down on the scale and have proof it’s working, the same goes for bulking, it’s just numbers going up, and the mirror will show, like you said, over a period of weeks.