My last Landcruiser spent a heap of time in the 10 years I owned it (vehicle was 13 years old when i sold it) visiting various beaches here in Australia, and hence got plenty of salt and sand on and in it....all I ever do is flush out the entire underbody and wheel wells etc with heaps of fresh water after I get home from the beach (or in the following days) aswell as wash the outside of the vehicle....previous vehicle showed no ill effect from all that salt. Usually I will back the vehicle up on car ramps under the rear wheels and go to town with a hose to remove the sand and salt...down the chassis rails, in the door sills, everywhere i can hose basically...the following weekend I usually try to do it again....all I mostly use is fresh water, though in the first few years I owned it I also sprayed (with a multi directional hose on a spray gun) Shell Ensis into the chassis rails, door sills and in the doors themselves (was a very messy job and car smelt for abit). I sprayed that stuff maybe 4 times over a couple of years into those locations.
You can't avoid salt when driving on the beach here, though I do avoid driving in the ocean itself (crashing waves that wash up on the beach or salt water creek crossings etc), but you certainly get salt spray from fresh water leaching out on the beach aswell as the salt in the sand...it's all part of being on the beach. I only got rid of the old Landcruiser as I didn't trust the engine, I had no issues with it's body or chassis after all that beach work.