Search for two keys close to each other which don't have keylocks and are convenient.
One finger shots the rope, the other releases it when you hear the sound that it attached to the wall.
You should start on a wxw or a "speed race" map really slowly. Just practice it really slowly and then change back maybe to one space that you are used to, not to get bored.
After about a month it is possible to go quite safe with it, and about 3-4 months you can reach the same speed as one space you had.
The advantages are that you can do the maximum speed that you can achive with one finger much longer, because neither your fingers, nor your brain gets tired so fast, since you will kind of halve (1/2) the moves of your fingers. And later maybe you can be even faster and still safe.
If you do it too fast that won't work, you mut to find the right tempo, start slowly and get faster.
thanks for response tomi. if i will play, for example, in online games with 1 space, and when wanna learn fr i go offline and practice there, will I improve my fr, if i will switching everytime from 1 space to fr, and back? sorry, mb, for the stupid question