Welcome to the forum.
Yes, SARndbox 2.8 is the recommended version.
In “I can’t make it rain”, you mention “1” and “2” keys. Did you assign these through the configuration file or the on-screen pop-ups? I recommend the on-screen assignment as a way to get immediate feedback whether the key assignment worked. Try adding “3” and “4” as more rain/drain keys through the on-screen assignment.
Once you have the keyboard rain/drain working, the rain hand is a matter of using the right hand shape.
Let me know if this works for you. There are other things to try.