Hi there, I think we need to clear up exactly what you are using the pressure barrel for and also look at the term secondary.
Secondary fermentaion on this board mostly means clearing tank, you take it out of the primary and you put it in a new vessel, leave for 2 more week and then bottle. Getting rid of alot more sediment.
When you moved your brew from primary to the pressure barrel did you add priming sugar? If so it will be carbonated after 2 weeks (roughly) after that you will only need the CO2 bulbs to help with dispensing. Is it a top or bottom tap by the way?
I only have 1 pressure barrel, a Hambleton Bard Beer Sphere, I only got it and my first attempt at a stout is in it right now, not quite ready to drink yet.
I do not believe you can force carb with these as they have pressure relieve valves to stop over-pressurisation. However i could be wrong on that.
If you did not add priming sugar to the barrel then leave it 2 weeks then bottle.
I have heard that these barrels are not too hot for lagers as they loose there carbonation very quickly, so I would be interested to hear how this works out for you, I put a stout in mine for the first try as it is not as big a deal if that is not as highly carbonated. Ideally I would like to use mine for lager so please post back as to how it works out.