I'd like to know what the effect of trying to bottle 35 pints of a light ale that's already been primed in a barel would be? Presumably there is still yeast floating about that would be able to convert a new dose of priming sugar for bottling? Might two lots of priming affect the taste? This is a hypothetical question... for now :)
I have done this many times with a counter-pressure filler. I have also used the Blichmann Beer Gun with success, although I think it does lose a bit more carbonation than the CP-filler. OTOH, the Beer Gun is much easier to use. The key to success is to make sure everything is very cold: Put the bottles in a freezer and take them out 6 at a time as you are filling. Cool the beer down below 40F before starting.
I'm assuming you are meaning that you've primed AND carbonated in the barrel. Correct me if wrong.
You can bottle already carbonated beer from a keg using counter pressure to reduce foaming. Our very own @joefish made a great video about the process he uses. https://www.youtube.com/watch?v=XXhYmTlHH50.
From a barrel may be more difficult being as you have little to no control over pressure and you may end up with a under carbonated bottle as a result of co2 loss.
I wouldn't reintroduce more sugar into the beer because then you may end up overcarbonating and have all the risks that go along with that.
As far as effect on taste. 5oz priming sugar has a 0.002 effect on your gravity so its hardly anything to worry about.