Getting SSS on a level is not that hard after beating the game multiple times and finding all collectibles. Just make it quick and keep the style meter as high as possible (most of the levels actually don't even require S+).
The real challenge is mission 17, where SSS requirements are much more strict than for other levels. Basically, you have to run like hell and keep the style meter maxed out, especially in the first bigger fight and in the last one. The trick for me was to use demon evade a lot, because it gives greater power for a moment. You can see it's activating when the time slows down for a bit and Dante's hands start burning. It's a fantastic way to get SSS in a split second by gathering and attacking multiple demons at the same time. Also, this strategy is especially effective against "ninjas" - use demon evade when they jump out of their teleport and quickly attack with Arbiter. It deals a massive damage, which means "ninjas" can be killed in just a few hits. Throwing Arbiter is not a good idea though, "ninjas" can easily turn the attack against Dante and break the combo.
After learning how to use demon evade it becomes a second nature, however for me its effectiveness drops down in tight spaces.
Good luck!