I hate to be that guy, but...
This isn't a flamethrower. Its a nicely packaged but overpriced medium size propane torch.
I use a more powerful one to weed my gravel driveway. It cost about $60:
https://www.amazon.com/dp/B00004Z2FQ/
It runs off a BBQ propane tank.
A military flamethrower squirts a burning liquid a considerable range, which can bring fire into fortifications, and stick to its targets while burning.
[Edit: spelling is hard]
The harbor freight one costs less but if you want an option from amazon this is a good one. Just toss it on your your grill and sear away. Getting the meat completely dry is pretty important.
Just get one of these https://www.amazon.com/dp/B00004Z2FQ/ref=cm_sw_r_cp_apa_fabt1_4f-RFbCYVJJAB
Don't you think that fire would be a more effective and quicker option than the one you are using?