This might be a fairly long check:
overview:
'Golduck is the face of rain in PU along with Poliwrath and Beartic.' - beartic is not at all a staple on rain as many use armaldo over it
'which it usually finds an opportunity to set up due to decent bulk' - its bulk isnt that great and it finds more opportunities by forcing switches
'However it faces competition from Simipour here' - it should only really be compared to poliwrath as you cannot compare simipour to a sweeper (the salac berry set is p bad)
'It also faces competition from Poliwrath as a swift swim sweeper, who has a more useful typing.' - you need to give a reason to why use golduck over poli
moves:
'If Golduck is already on a rain team with rain support, then it can run Scald instead of Rain Dance as a reliable STAB move that still OHKOes most offensive pokemon and has a useful burn rate. Surf is also an option if OHKOes on Stoutland, Drifblim, and Barbaracle are wanted.' - i disagree with this as even on rain teams you want several setters + scalds burn is barely relevant as not much can take a rain boosted lo hydro (also dont mention pokes like drifblim in analysis)
sd:
'such as against Tangela and Gourgeist after Stealth Rock damage' - you have a very low chance vs gourgeist
UT:
'If using on rain teams, Golduck is best sent in when the rain is up and when its checks or counters are weakened or removed, allowing it to cleanly sweep the opposing team' - i dont see why this is the case only on rain teams as on non-rain teams you are using this as a cleaner whereas on rain teams you can either use it as a cleaner or a wallbreaker
'Golduck has okay bulk but it should be wary of setting up in front of strong attackers like Ursaring because they can either KO or put it in the range of death due to Life Orb recoil' - instead of saying 'be wary' either say 'do not' or just remove it (you dont have to say 'dont set up on pokemon that OHKO it' as its fairly obvious)
'Avoid setting up on pokemon that commonly use status moves, such as Grumpig, because thunder-wave and toxic will severely cut down Golduck's sweeping ability.' - you just said to set up on defensive carracosta which almost always run toxic
to:
'Golduck pairs well with special wallbreakers, such as Simipour with Low Kick or Knock Off, Nasty Plot Ninetales, and Simisage, who lure and weaken special walls like Lickilicky and Togetic that can switch in on Golduck' - golduck has poor synergy with simipour
'Toxic Spikes also works great to wear down special walls' - can you word it to make it sound relevant as currently its very generic as toxic spikes wears down every pokemon
'Pokemon such as Swords Dance Armaldo and Swords Dance Beartic can lure and KO Poliwrath at +2.' - 1) these two are listed in other swift swim users later (please dont tell me you mean non ss sd maldo/bear) 2) i dont see why luring poli is too important if you already do 70% to it
'Other water types such as Specially Defensive Pelipper and Politoed can be lured and weakened by the likes of Ninetales' - politoed isnt relevant
'Electric and Grass types like Leafeon and Raichu can handle these water types' - by 'these waters' the only relevant one golduck has a problem with is pelipper which doesnt care much for grass types
'Knock off users such as Carracosta' - knock off costa and rd golduck dont really fit on the same playstyle
oo:
'Hidden Power Electric could be used on the rain dance set specifically to OHKO Pelipper and Swanna, but they are already 2HKOes by Hydro Pump anyway' - this should be reworded as sdef pelipper isnt 2HKO'd
i dont think synchronise should go here but w/e
'A Calm Mind set with either substitute or encore makes a decent sweeper, but Golduck lacks set-up opportunities' - i wouldnt say 'decent' and the main problem with that set is its shocking speed meaning you better off using np simipour
'A Calm Mind, rest, sleep talk, scald set may be tempting because it is similar to Suicune, but Golduck lacks the bulk to pull it off. Golduck can make a decent wallbreaker with four special moves but it is outdone by Simipour, who is faster.' - if its an outclassed set you shouldnt mention it here (also same with cloud nine)
'Hone Claws used with Hypnosis can lure and put asleep Golduck's counters, but is gimmicky' -remove this as regular golduck doesnt exactly have many counters which cant be bopped by other moves and you lose all ur utility
cc:
firstly the format should be like **Special Walls**:
Secondly you shouldnt mention bad mons even if they are decent checks (ie politoed/lapras/possibly gogoat)
i dont see why you are mentioning life orb recoil in priority and it isnt bothered as much by encore than by thunder wave (volbeat/krow arent exactly the best switch ins even if predicting rain dance)
ManOfMany