Nails installed with a properly adjusted pneumatic nailer are less likly to split. That's partly because fence nails are box rather than common but fast insertson is the real key. Hardwood trim sometimes must be pre-drilled to allow hammer driven nails.

If you are indeed useing Redwood,you should use stainless nails because even galvinized will corode and stain before the wood rots.

+1 on using stainless. Try filing the points off the nails before driving them with a hammer, that seems to reduce splitting a lot, at least in nailing shingles and clapboards. Failing that you may have to pre-drill.

Ive been using deck screws of various lengths - including short ones for attaching panels. Like that they pull the wood super tight together. Sounds ike you got good advice above though specific for redwood.