There is a certain protocall to waving when you reside in a rural area.
Furthermore~you will receive more waves IF you are driving a truck.
It matters not what make, model, or the size...but it needs to be a truck [tractors are even more 'wave' friendly].
You can give and receive waves while driving a sedan, but unless the other driver actually knows your vehicle very well, this is not as likely.
I've been driving in Vernon County, WI since 1996 and have studied this phenomenon.
There is the one finger wave which is Acknowledgment.
[you give or receive this basically to just give 'nod' to the other driver]
The two finger wave is a bit more Formal.
[you give or receive this probably with a smile and a nod]
The 'hand' wave is very Friendly.
[this one is more complex as you do not remove your whole hand from the steering wheel~but you are giving a nod, smile, ...and probably even know the other person. this is purely a back road howdy which can sometimes result in the two parties ~~ if both gave the hand wave ~~ stopping for a bit to chat and catch up on the local gossip]