Holding the can upside down is the very least of your problems. If you have already put in the leak sealer, I'm afraid that you made a HUGE mistake. Once air hits the sealer, which is immenent, it will gunk up every component in the system. The only way it will ever be fixable would be to replace all components.

You should NEVER just start putting refrigerant into the system without monitoring BOTH low AND high side pressure, most especially a converted system. The high side pressure can easily get out of control.

I don't see anyway out of this mess without breaking federal law.

Best of luck,