The in game command list actually gives instructions on how combat assist works and breaks it down into Openers, Linkers, and Enders. So basically pressing f+button will get you the easy mode for whatever corresponding move you're going for.
So if I hit someone with a cancelable normal I can press f+MP to get my character's easy special assigned to that function (opener), whatever it may be, then I can press any button I want to get the corresponding auto-double or manual which is the same as playing standard. I can then press f+button to go into a corresponding linker, then another auto or manual, etc. Finally ending combos is done with f+HP or f+HK.
Combat Assist will not do manuals for you, they will always be... Well, manual.
Mashing is a bad idea regardless of which control feature you're using, and no they don't come out faster.
One correction for the above: once you're in the combo sequence, you no longer need to hold Forward to use a linker.
For myself, I do my own Opener (let's say Cyber Dash with Fulgore), and then I rely on the Combo Assist system to not have to do directional inputs and I simply press the various punch/kick strengths that I want to keep the combo going. I'll adjust the strengths based on the tendencies I see my opponent trying to break. If they lock out, I stick to Heavy's or Shadow Moves. I then manually input my own Ender.
I also like how you actually use the Heavy buttons in the system to do the Heavy moves, instead of having to hold Medium Punch or Kick for the Heavy.
I do mix in Manuals sometimes as well, and no
@DeftMonk , Combo Assist will not perform manuals. You can fully read how it works on the official blog post
here.
What blows my mind with Combo Assist is the level of hate it seems to get, despite being such a well designed system. The only thing it's really doing is removing the need for inputs in the combo system, thus reducing drops. If used fully, it's actually quite limiting as a combo will be predictable, there won't be any manuals included, it only permits two kinds of enders (and typically not the damage one, and most players relying on it fully won't know how to capitalize on a launch or wall splat), and if you don't have a fundamental understanding of the game's combo system, you're either going to be ending your combos far too early or you'll regularly blow them out! Button mashers will blow out all the time because they're not controlling the combo, they're simply mashing with no thought for the system and no strategy.
Combo Assist also does not natively allow you to use your character's Combo Trait, you need to manually hold Back to do so. This part of the system doesn't seem well documented, for some reason, but for, say, Jago and his Around the World trait, that's quite limiting.
As the other player, all the rules are still in place, and you can still Break and Shadow Counter any Combo Assist combo.