The British Museum would not need to coat their coins with anything - Fisrst the coins have already undergone extensive conservation and any stabilisation , if it were needed.
They are also storged under more controlled conditions than the regular collector.
The renovwax method was tried and discussed in another group I belong too. It basically takes a cleaned and conserved coin, immerses it in a hot melted wax for several hours [read a day or two] until the very liquid wax can saturate the coins crevasses, then the coin is removed and the excess wax wiped off. If the BD is not fully neutralized first, any moisture that may
work its way through the wax, will re-activaste the chemical reaction, wich will continue un der the wax layer, so nothing would be gained.
I do use renwax, especially on 19th and 20th century medallions, it does not effectthe visable
patina, but will remove finger oils, and minor oxidation on the surface. this has the advantage of leaving the basic coloring [
patina] in tact, but removes the harmful surface contaminents. I also like the ring fitted Air-tite containers, as they keep thing from sliding & banging around and being worn [often call "coin cabinet"
patina], and they are easily opened if I need to re-scan the item.
Bruce