Perhaps I should have added that in those contests and shows a cardinal rule is/was that ALL work must be that of the entrant. Buying a builtup, buying a paintjob, or getting somebody else to paint and/or assemble a model is an immediate disqualification. The contests are intended to promote competition among hobbyists, not professionals or the Danbury Mint. (We also do not allow unaltered die-casts.)
The only contests I've ever entered, and ALL the contests I'm involved in presenting, require every entry to be the sole work of the entrant. So shared builds, 'bought' paint jobs, purchased models are prohibited. I don't know of any that allow an entrant to buy an entry or any substantial portion thereof.
Each of the contests state the cardinal rule clearly, and each entrant understands that disqualification is the penalty for violating the rule.
In the example cited, where the Skill 2 Guy enters a model and declares it was painted by someone else, the model would not be permitted to compete. It could be displayed, but would not be judged. If Skill 2 Guy does not declare/admit it was painted by ProSprayer Guy, it would be disqualified upon discovery.
The idea of buying a build by a model seller ~ or buying a paint job from a professional painter ~ and then entering it as one's own work is cheating, plainly and simply put.