Do you mean posting on their post or just speaking to them? I'm sure theirs no problem with speaking to them guiding them what to do, but posting on a un-ban appeal is not allowed as far as I know.
What is written must come from them. Sure you can give them pointers and help them get the right words and wording as English isn't everyone's first language. Personally I don't advise going out of your way to PM someone saying ' yours appeal will get denied because of lack of effort/improper explanation blah blah blah' as it is THEIR appeal. If they show lack of effort that's their own fault. If they show lack of understanding we can attempt to enable them to understand, or gain a clearer understanding. It's better for it to come from us (staff) as your understanding of the rule might not be in line with the rules themselves.
Bumping is commenting before a staff member has responded, or adding almost/pointless information/dribble/ literally writing 'bump' or something to the same degree on a/series of comments.
OR its writing a new appeal whilst already having an appeal open.