I will not second guess Fernand; he knows his stuff... but will say I revere my Provari's since they first came out. I've had at least one since 2010, and love having my V2 (sorry this is a Vapage thread, but imo VV Tube mod is not same species as the XL Vmod B/F). For those of you that don't know the science of it all, the internal meter of the Vari has taught me everything i know about vaping.
I may put Fernands method for the 357 on the XL to use someday... 'til then I keep an Aero on my XL, which along with the AVA i have found to like on an other hard hitting VV, are the only other atomizers besides the HH357, that I really like. It's smooth and hassle free.
BTW, Hanna says not to blow from the d/t side of the 357, but "gentle", as Fernand says, shouldn't hurt. Another way to blow it using an XL would be to take if off and blow from the recommended threading side.
IF you are getting "gurgle" and little vapor, it's over fed = flooded = not good. Less is better although I'll repeat; dry hits are not a good norm. Over feeding is why it's taken me so long to get used to bottom feeders, but then it took me a while to realize that was the problem; it's very simple really.
IMO the HH357 is the best atomizer available today but forgive me if I sound condescending when i say, you have to have a pretty good understanding of "the care and feeding of" an atomizer. In other words if you know how to drip.