You're saying "racked beer," so I assume you're already planning to rack it from the fermentation vessel/carboy to a bottling bucket. If that's the case, just pour the corn sugar solution into the bucket before racking the beer. Then when you rack the beer into the bottling bucket (carefully), the wort will mix evenly with the corn sugar. I wouldn't add the sugar last, because then you'd actually have to stir/mix it to ensure it's evenly mixed.
If you're going from carboy directly to bottle...I guess the carbonation tabs would be the only way. I'd certainly recommend going to a bottling bucket, though. It will ensure even mixture of the sugar, and any trub that gets sucked up (there will be some for sure) will be mixed evenly in all the bottles, instead of highly concentrated in just a few bottles.