Sorry for not answering your question as I haven't tried using external drive in PS4. It should be quite straight forward though, just make sure you don't buy the slowest device on the market.
However I think the long term solution would be better if you would upgrade the internal storage. The drive is really easy to change, they have designed PS4 so that you can do it without any expertise.
Just buy something like 2TB HDD or better yet SSD drive and you're set. It might cost you even less than buying external drive with the same capasity. After that you don't have to worry much about what you want to install on your PS4