thing w/ Atoll attacks is the 6k-point stacking limit, the auto-shock attack, & supply spoilage.
1) bring your best guys (USMC RGT, not USA; 155 ART BTN, not 105; M4 tanks, not M5s).
2) full planning prep for the target, also an AGC in the TF to help speed unload.
3) as much Naval & Aerial bombardment of the target as you can provide, prior to the invasion.
4) full interdiction of enemy re-supply during the pre-invasion period. in-range DBs should search/navattack around the target, w/ ground-attack against the target as the 2ndary mission.
5) run the AmphTF into the target hex, Remain on Station & Do Not Unload. (of course you've already swept for mines, and have near-complete air superiority.)
6) then you can unload/assault in the subsequent turn & have 4 full amph-unload phases to unload before the ground-combat phase. the AmphTF must include DD/CL/CA/BBs to suppress enemy gunfire against your assault. (lighter ships w/ less than 5" guns need not apply for this role.)
7) note the turn-sequence. you get 4 unload-phases, then ground-combat, then spoilage.
8) if the initial assault is not successful, you've got several options. both sides likely took hvy losses, likely the defender's fort-level was reduced. if you've got viable AV on the hex, you can task it to assault again, even if it's got no supply. b/c if you've got add'l amphTFs in the hex, you can task them to unload - they'll have 4 turns to unload before the next ground-combat.
9) you can set your on-target troops to attack, or defend. you can set your reinf troops to land, or to wait (new troops unloaded will trigger another shock-attack). you can set your supply-ships to unload or not. new unloading TFs will need gunfire-support DDs (or better) if they are to survive enemy fire.
atoll-invasions require that you prep the target w/ heavy preliminary bombardement, bring enough 1st-line strength to banjo the enemy on your 1st assault, and have add'l support immediately available for re-supply.
I would add that you should put old BBs in your invading TFs as they will soak up the shore fire and deal out nasty counter battery. I find this better than using them to bombard.
And, for later on, the rocket firing Allied LCIs do work and are a must in your landing craft or barge TFs.
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