I have 2 discount brokerages I use, but, you're correct, they would not accept penny stock certificates because of all the new SEC and FINRA rules to weed out counterfeit certificates.
You MUST fill out lots of forms.
You MUST PROVE where you got it from, as well as HOW you got it.
Did you pay for it, was it a gift, was it payment for services rendered ? What, where, how, etc ?
PLUS, forget about just sending it to an attorney for an Opinion Letter, and then to a Transfer Agent to have the Legend removed.
Whoever told you that's all that's involved, uh uh, because if you do that, when you give them to a full service brokerage, they will make you send it BACK to the Transfer Agent to have the legend PUT BACK ON, then back to the brokerage for THEM to control the entire process.
You must deposit the certs with all paperwork with a full service broker that has the capabilities to do all the steps necessary to fulfill it through to being made good to go.
For one only, from only one company, if you had an attorney that would do it for what I had it done for, still almost $500. Maybe a little more overall if more than one at the same time for one company.
But it has to be worth converting to free trading.