Salt I had everything wrote up and deleted it and now I am going to write it again.
If I were you I would start them in a warm house in cups and as they sprout put them outside in the day and in at night.
My reasons for this is two fold.
Snails and cold nights.
This will increase the sprouting time a lot and when you plant them out they will be bigger and more able to deal with a critter eating on them.
I am dragging all of my information up from growers in the UK as I feel they know more about runner beans than many people in the US.
Okay I could have sworn I saw runner beans now I see pole beans.
You can do the same with them too but my Kentucky wonder I just planted out.
And some others I planted in containers.
Right after I plated them out the cold snap hit then the snails hit.
Some made it through but some the snails or a darn bird ate back.
As far as soaking I see no need to soak a bean seed.
If the soil is moist it will be the same either way in 24 hours or less.
Worth