I find vaseline on feet is good - but if you are going to tape, do that first! lesson learnt on first ultra I did!!
The OMM is ALWAYS wet - guaranteed, never had dry feet in any of the ones I've done!!
I had great success with the basic Injinji socks on the SDW race this year, hadn't really trialled them before race.
I also have several pairs of Pete Bland £5 merino wool mix socks I wear for my winter running (winter running involves snowmelt puddles and bogs and occasional wading of rivers with snow melt). They are not perfect but are the best for keeping feet warm, even when wet ... and are sooooo cheap.