I used to run 3 Attack Natu with U-turn in combination with defensive Mienfoo and Choice Scarf Chinchou. It was pretty darn good at keeping momentum, but I have no illusions of it being particularly good, beaten fairly well by Misdreavus, which is why I ran an Eviolite Houndour.
Fast Natu gave me the ability to check defensive (or otherwise non-max Speed and Stone Edge) Mienfoo, as well as doing considerable damage to Timburr, while countering Ferroseed and Bronzor and KOing Ferroseed with Heat Wave and 3HKOing Bronzor.
Bulky Mienfoo isn't really worn down by entry hazards due to Regenerator and gave me a solid counter to most DD Scraggy. Knock Off lets the core's U-turns and Volt Switches do considerably more, stacking up with Stealth Rock damage. Finally, I ran Hi Jump Kick on it over the standard Drain Punch to let me always OHKO DD Scraggy, which is otherwise a massive threat.
Choice Scarf Chinchou isn't amazing, but hits a lovely 24 Speed, letting it outspeed +1 Magnemite and Dratini, as well as +2 Tirtouga, and KO them all (when not holding Eviolite). Checking Tirtouga is huge, and just using Volt Switch lets me keep momentum if they play safe and switch out. It's weak to Diglett, but eh, with Team Preview it's often fairly obvious when it'll come out, and it's OHKOed by either of Ice Beam and Hydro Pump. Being resistant to Flare Blitz and immune to Wild Charge really helps against Ponyta too.
Seeing as this core is weak to Misdreavus, especially Calm Mind RestTalk Misdreavus, I ran an Eviolite Houndour, which with prediction checks every variant reasonably well, as +0 Hidden Power Fighting never OHKOes. SubRoost Murkrow also beats most Misdreavus (sadly again requiring some prediction) and it really benefits from the racked up damage the core causes. It can also check Double Rush, to which this core is very weak, but yeah, it's really a gaping hole that the rest of the team needs to fill.
Double Rush cores are just about the hardest to deal with in the metagame, as very little can check the duo and
not be taken out easily by teammates. Choice Scarf Snover switching out takes a minimum of 50% from offensive Munchlax, and Porygon fares little better, taking 46%. Even if not using Munchlax, something like Frillish can easily switch in—Porygon/Snover is forced
to use an Ice-type attack—take the resisted attack easily, and Recover/Scald/Will-O-Wisp. Specially defensive Lileep in sand is not even a guaranteed 3HKO with Ice Beam from Choice Scarf Porygon, and can Recover and Toxic to stall it out.