Can be hard with the IP restrictions that go with most employers. The nice thing about something that's pure marketing & writing is that for software developers, it probably does not fall under your employer's umbrella.
One good reason to seek out employers that dont' have all encompassing NDA/IP restrictions as part of their hiring contracts. They're hard to find but they do exist, and they're worth their weight in gold.
It's much easier to get the negotiating leverage to strike out IP restrictions on your contract if you've previously worked at a name-brand company, and name-brand companies are the ones that tend to have the most all-encompassing IP restrictions.