0 - 30 Buy from NPC
30 - 50 Use a 30/30 tinker box (create a new char with 30 tinker/30 carp)
50 - 72 Use a 50/50 tinker box (create a new char with 50 tinker/50 carp)
72 - 94.7 Use a GM tinker box

Using a single box, use a macro like this:

If (SysMessage "appear")
Double Click (key)
Wait for Target
Absolute Target (your box)
Pause 1.00 second
End If
Double Click (lockpicks)
Wait for Target
Absolute Target (your box)
Pause 3.00 second