CEP Amp Air ! Have heard great things about it and we use sev of their other products with great results 

I've been using CEP amp air. While I don't really feel like it gives her a ton of extra 'edge,' I WILL say before using it, if we were warming up or running indoors she would cough a few times to clear her airways. She doesn't do that anymore. 

I used Flair strips and OE Wind. 

ETA: also used Oxy-Gen and liked it as well, just liked that I was fairly often able to get OE on sale. I don't know about now as I haven't ran barrels in a few years, but I was a firm user of Flair strips and either OE Wind or Oxy-Gen