I'm interested in the Oil idea for the wood deck. I'll have to look into that.
Depending on the look you want, can use old engine oil, fresh oil, or I also hear that red ATF works very well.
This is best done in the heat of Summer. Apply oil to wood until the wood won't accept any more. Let oil-soaked wood sit in the sun for 2 to 4 days to really soak in. If you want, place cardboard boxes under wood to catch any drips. Most importantly, soak all sides and edges. End grain will soak up the most.
Once oil has soaked in and been sun-baked for couple of days, you won't have to worry much about wood being slippery. If needed, use a router with 1/2" straight bit, and cut a diamond design with diagonal cuts 1/4" deep and about 1 1/2" to 2" apart for traction.
Another option that many don't know is burning the wood. You can take a propane weed burner (ANY time of year!) and scorch the wood on all sides until pretty much black. Use wire brush in drill or angle grinder to remove most of the char. This helps to seal the wood from moisture as well as repels bugs. I just learned about this fairly recently so have not had a chance to try it, but there are many videos about the process. Check here:
shou sugi ban wood burning - YouTube Some good videos out there, but also lots of boring ones from folks who only repeat what they hear (....like ME! *lol*). I'll likely be trying this on a small trailer over Winter or in early Spring.