Most signature campaign managers don't do that. Let me show you the prerequisites/rules for applying for a signature campaign by a few reputable managers:
1.
icopress:
➥ Any application will be
ignored if it does not match the template.
➥ Do not send me your application by PM and do not ask why you were not accepted
[1], [2], [3].
Whale username:
Segwit Bitcoin address:
2.
Little Mouse:
11. If you are accepted, please wear signature, avatar, and personal text. Check out the spreadsheet whether your information is correct or not.
3.
AB de Royse777:
HOW TO APPLY
Reply to this thread with the following information
Forum Rank:
Bech32 address:
4.
Upgrade00:
How to Apply:1. Fill out the form below as a reply on this thread,
Bitcointalk username:
BTC Address (should be SegWit):
If you notice, none of them has it as a prerequisite for participants to wear the signature and avatar before applying; they might have it in the rules or requirements for participation, which is a different thing. And, even if a manager does ask the participants to wear them, it doesn't mean they won't accept those who didn't do so, but it's just a term added to encourage interested participants to do that beforehand.