Just to clarify :
The
Mask technique was a special application of
Sith Alchemy. A
Sith Alchemist could use the Mask to literally reshape an individual's appearance, altering a body at the molecular level. Very little was beyond this technique, limited only by the craftsmanship of the user. Features, age, disfigurations, even species could be concealed with the Mask (though the latter would require an incredible amount of skill to accomplish convincingly). Owing to its molecular nature, the technique lasted until altered, and even a thorough medical examination would not be likely to reveal anything out of place, unlike the tell-tale scars of surgical alterations. In fact, not only was a Mask more convincing than cosmetic surgery, but it was also horrifyingly faster: a skilled alchemist able to alter an appearance in mere minutes (provided the necessary materials were on hand).
Daxton is not yet skilled enough to mimic another specie but he is skilled enough to appear as another Zabrak. The only way you can know it is him is prolonged study and knowledge of his unconscious ticks, and only if you know him very well. Otherwise he looks, like a completely different Zabrak.