I'm also in the midst of practising like mad with Chris' 5/5.5G pick.
I found the Union 2134 to be a good start. Then someone suggested a Legge Value as a good practice lock. I'd already found one of pinky's Legge Value locks, with low levers in two and four, to be pretty challenging. And then my practice Legge Value turned out to be almost identical. It took four hours

(sat in the living room, bored with the vice and the bench - I'm also teaching myself to practice the Chris B way - he holds the lock and tensions it with one hand, and picks it with the other).
I can open all of my (four) practice 3G114s and 3G115s faster than that! Although for me it's harder to get out of anti-picks with the 3g114/5, it's easier for me to tell that I'm in them.
My ERA Invincible practice lock has a silly lever pattern. They're all in the middle - 3s, 4s and 5s - you just lift every lever by exactly the same amount and it's done. I've just got myself Invincible low and high levers to make it a bit more realistic. The ERA Profit is 7G so unless you're splashing out on more than just a 5/5.5G CB pick, it's no good yet.