I'm glad you posted this because I'm thinking about getting a pelham( stupid question but how it that pronounced ?) for my mare, she is really good for me but every once in a while she gets fresh and runs through the bit. I've never used a double rein before so I was looking for some tips. I have the same problem with everything saying to bit her up only they advise corkscrews and twists instead of the TT
I found that with the 2 reins, what works well for me is to have the snaffle rein between my middle and ring fingers and have the curb rein between my ring and pinkie fingers. Then when I need to use the curb, I just slide my pinkie up over the curb rein and tighten my hands. Obviously that's not "the proper" way but it works for me since I'm not showing or anything... It might also be different for me since I'm using western reins. I have one 10ft, thick, "roping" rein for the curb and a 8ft, thinner, "gaming" rein for the snaffle. The 8ft rein is just long enough that I have contact with Lacey's mouth pretty much all the time and the 10ft is long enough that I can hold it but have it never engage unless I purposefully choose to engage that rein. I kinda like that because it makes me engaging that rein all the more shocking to Lacey (because she's forgotten about it) which ups my "magical powers" quota. And because I'd like to eventually be able to go back to something gentler, if possible, I don't want her to get too used to the curb rein being "on" all the time.
However, in your case, it's probably different. :)