Hi Ian,
I use Adorama VC RC paper negatives to make salt prints quite often.
I doubt they will take wax, but you should be able to make nice salt prints without waxing them.
Thank you, I feel better about using my Adorama VGRC. My negatives were good, they scanned a nice image without any curves needed. My silver nitrate was 10% and citric acid was 5%, applied to arrowroot backer. The brushmarks on the salted paper outside of where the negative was covering became chocolate brown in only 10 minutes. Nevertheless I now suspect my silver nitrate which I mixed fresh. I will try some old stock from collodion work, not as strong, but it is "seasoned" from use. Do you add a drop of iodine to the new silver nitrate or anything like that to season it? Maybe California is closer to the sun than Virginia!