I suggest you contact the Brazilian embassy in China near you with your questions (Beijing and Shanghai seem to have embassies). I believe their answers are more accurate than those here.
If you are only going to Brazil for business investigation, you might as well be invited to the company instead. Although you are invited to go, you can write down your official position and get a higher visa pass rate.
As for your handwriting, in today's society, most of them are printed and stamped, signed by hand, and basically you can't see pure handwritten documents.
After the invitation letter is completed, it is best to send you a copy by email at the same time as the original, so that you can go through the preliminary formalities first.
As for the visa application materials, generally speaking, you need a certificate of no crime, a birth certificate, a certificate of work income, a passport valid for at least six months, and some may need academic credentials. The above documents, except passports, need to be public documents.