All the Approach's are match specific, Depending on what character your playing vs. Pill rushing is def one of the basics you can use against (almost) any char and get close enough to take advantage of Docs close range game. You still needs to remeber -It's all about the mindgames!- You can learn how to rush in or do whatever tactic you like, but putting it to practical use in matches against good opponents is key.
Example - With my style of play, vs Space animals its a very defensive style of approach. Double jump pills to escape shffl'd anything, into Dair / FF'd Nair. If they get too noticable of the idea, I switch it up to a short ground game with more speed to mix it up enough where they have to adapt to the new playing style. Your approach must always vary to add to the mindgame, so you have to mix up your game.
You always need to take into consideration the level of skill your opponent has. Some people will fall for dumb mindgames and others will just counter with ease. Always be patient and watch his gameplay a bit so you can understand what he trys to do.
I've Learned to make up new approaches and retreats depending on the match-up to confuse and take my opponent out of his norm.
It's all about the mindgames.