How to good working knowledge of tax in articleship?

Try changing the department 6 months or 1 year later. If that's not possible, just browse through the discussions in ca club india tax sections, select few queries you have little knowledge about, look up for them in the internet or books or bare act, analyse, answer the queries and get corrected by the other experts' answers in case you have gone wrong. You can gain much more than it appears. You would be left only in filings of ITRs and tax audits. You can also fill them up hypothetically.