First and foremost watch the freakin pikimin. That is standard vs Oli period. Depending on his line up certain options are more favorable. Think of it as soft determinism. Learn the clanking properties vs his attacks. Sonic's nair can go through even yellow usmash if done properly.
Wedge I would have to disagree with fsmash not being good to kill. It can be used in the same way as dsmash although dsmash is more amazing at covering Oli's landing and auto dodging whatever he puts out ( its an amazing tripguard anti air). Fsmash can be used to dodge the small range on his aerials and to punish ADs. Land camping is really the name of the game vs this character. use uair frame traps or even just run to the landing watch. In fact you are having trouble stringing attacks vs Oli you are messing up, because that isnt the hard part of the MU.
The difficult part is getting in. we have ASC which is nice but can lose to pivot grabs and nair. I usually tend to ASC with the intention of hitting the top of their shield so if they pivot grab i still hit them. side b is also really good for hoping over grabs/pivot grabs and getting oli airborne. The real threat we have is him utilizing those things with a fsmash. Fsmash controls a good amount of space which is why u need to be somewhat familiar with pikimins ranges. yellow fsmashes range beat even sh approaches so be aware of that. However use things like side b shield cancel to get in on fsmashes so if you are having trouble getting in opt for that to get safe dash ins.
One thing we do have in this MU is punishing the crap outta Oli for throwing pikimin. This is HUGE. Go look at Oli's frame data
Latch
Hits on: 9
Ends on: 25
at mid range Sonic can react to a grounded pikmin toss easily. Even worse is when he sh pikmin tosses due to us having the arguably best land camping tool in the game in spin charge. This is critical against Oli because he needs to know that he cant toss for free against us. we could even just run in and grab if need be due to our run speed. This makes these easier for us because now we can relax until we get in mid range where we can pressure. sh bair is good too for an approach as well.
I can not stress this enough; WATCH THE PIKMIN. It makes life a ton easier and allows you to be aware of safety zones. Also be patient; impatience is so costly vs oli as he has VERY strong strings that coupled with any type of pikmin latch can cost you ~ 50% or something stupid in an instant.
The only problem I have with this MU whether I play dabuz, Richbrown, or local Olis is gimping. It feels exceptionally hard to gimp Oli with Sonic and I hate going straight up with a character with such strong kill potential. If you get an oli to the ledge space yourself pass the ledge attack of course and try to occupy space with sh bair while you're watching their habits. Sometimes you can get an misspaced ledge drop uair with a fsmash or interrupt a ledge hop with a dtilt> edgehog.
Also recently I have been creating some setups with spring drops while attempting to edgeguard Oli forcing him to deal with a spring approximately by the time we have already landed with a good edgeguarding position. I have gotten some good edgehogs smashes and resets from this so I definitely think its something to be looked into. oh and our bthrow is so beast in setting this up and even in general in this MU so dont be afraid to deviate from uthrow in this scenario as it sets up a ton of good land camping options.
Oh and uhhh DA is KINDA GOOD and when I say kinda, I mean immensely so.
RUSH HIM DOWN. It should look combo video style once you get him airborne
me vs Rich
http://www.youtube.com/watch?v=Isbi-jtMXNI
Espy vs Denti
http://www.youtube.com/watch?v=yvu42xPABF4
http://www.smashboards.com/showthread.php?t=224450
Know your Pikmin.
know your frame traps and land camp options.
We also need to elaborate on what tilts we can use for spacing as due to the properties of oli's grab, you can do things like dtilting at the tip of his grab range and if he attempts to grab he will be hit by the dtilt as he pulls you in. This is definitely something to be aware when fighting Oli.