The most effective way at getting through the pain period for me was to Anki about 2000 sentences (both reading and listening cards for each sentence) and have

The most effective way at getting through the pain period for me was to Anki about 2000 sentences (both reading and listening cards for each sentence) and have that cover all the way up to upper intermediate level grammar. Doing so gives you a base of about 1500 ~ 2000 vocab at the same time. After that progress takes off if you acquire vocab as fast as possible while speaking to natives as much as possible. That initial bootstrapping phase can be done in 4 months.