OP - bottled flat beer, not wort. If you bottled wort, then I'd suggest it isn't just priming sugar you forgot.
jajao44 is right on if there is some carb you might want to give a few more days. Sometimes just stiring the yeast can cause a little more wort to ferment PLUS what if you are just up a priming sugar pack? (I know doubtful, but caution with bottle bomes seems prudent here)
Duboman has a good suggestion - that is mixing with water and putting it in the bottles. Your suggestion of putting all the bottles back in the bucket and repriming and refilling is the generally listed on in the books.
IF I were doing it, I'd try the eye droper. I'd be a little concerned about head space in the bottle (I usually leave a few inches, although I notice commercial brewers leave almost none). Walmart has a plunger/droper in the medicine area for dosing out liquid medicine. I think it is like $2 or $3 and has a max size of eithe r5ml (1tsp) or 10ml(2tsp). With this you could quickly fill and empty it into your bottles and be sure you got a constant amount of liquid in each. I don't know how much you want to add to each, it depends on your final priming solution volume and the number of bottles you have. A typical cup of liquid is about 240ml, so with 48 bottles youd do 5ml each (5*48=240)
good luck