I have used the TLF reactor For BP. Just be sure to buy the screen kit. Just add pellets slowly until your nitrates go down to where you want them, then mark the level of the BP's in your reactor so you know where to fill it up to when they break down.
IMO a specialized reactor is the best way to go. A BP reactor will allow you to adjust not only the rate that the pellets tumble but will allow you to adjust the amount of water that enters and exits the reactor. It's important for the pellets to tumble and as the pellets wear down they need more flow to tumble and if you just increase the amount of water going in and out of the reactor then you are increasing nitrate removal. I ran BP for a year and a half and that was the problem I would have. I now use vinegar with a doser to get the exact amount of carbon I want into my tank. There are many whove had success with BP I just wasn't one of them.