Rubber patch here.
All that jazz about burning the leader? I get it, but the bit of heat created in the process is what helps straighten the leader. It is important - basically, you are establishing a new memory for the leader.
My solution to the "burning problem?" Don't zip it through so fast.
We finesse everything we lay our hands to when fly fishing - but we cant "feel" our way through this one?
Pulling leaders through my hand, over my knee, around my ear or just tugging on i hemgood and hard... none of these has done the job as nicely as the rubber patch. They're alright in a pinch, yes.
But I just use good old-fashioned contact cement to glue a piece of rubber to a couple of leather patches. Join them on a split ring, hang on my vest and, "Voila!" its a done deal.
A lot of things have been improved down through the years, but I venture to say this isn't one of them.
So far, the fish don't seem to care that I use it and I have not broken a leader because of it.*
Besides, what is fly fishing without yet another gadget to hang on your vest?
* Now, my ability to tie good KNOTS... well, that is something altogether different! LOL