Pokemon can be painted more than once, and paintings can be replaced. It won't recieve an extra ribbon though, it only gets one of those.
As far as the requirements go for being painted, I've posted this accross several posts in the contest thread, so I'm mostly repeating myself, But I'll put this together for you. This will be a detaied explanation, But if you want the exact requirements here's what I've learned from
The Ultimate Pokemon Center
Primary Judging: int((Secondary Attributes + Luster)/2)+Primary Attribute
int() means to take off the decimal part. Computers don't like fractions.
Luster is represented by the stars going around the Pokemon. This is the sum of all the Feel of the Pokeblocks fed to the Pokemon. Max is 255.
Primary attribute is the contest you are entering. Tough, in your case. If that's maxed out, this is 255.
Secondary attribute is the two attributes the audience doesn't dislike. This is Cool and Smart for a Tough contest.
A scarf will add 20 points to the attribute it raises. (maximum 255)
(note: if toughness is already maxed, try giving it a red or green scarf, since the attribute cannot go over 255.)
This value gives the stars in the final round:
Final Stars:
0 -- 0 stars.
1 - 63 -- 1 star.
64 - 126 -- 2 stars.
127 - 189 -- 3 stars.
190 - 252 -- 4 stars.
253 - 315 -- 5 stars.
316 - 378 -- 6 stars.
379 - 441 -- 7 stars.
442 - 504 -- 8 stars.
505 - 567 -- 9 stars.
568 - 630 -- 10 stars.
Hearts are based off the total of the appeal scores.
Final Hearts:
0 -- 0 hearts.
1 - 40 -- 1 heart.
41 - 80 -- 2 hearts.
81 - 120 -- 3 hearts.
121 - 160 -- 4 hearts.
161 - 200 -- 5 hearts.
201 - 240 -- 6 hearts.
241 - 280 -- 7 hearts.
281 - 320 -- 8 hearts.
321 - 360 -- 9 hearts.
361 - 400 -- 10 hearts.
The final score is (Appeal score * 2) + Voting score.
the painter will paint your Pokémon if it wins a master rank contest with at least 800 points.