Rule number 1 when fighting multiple large monsters during a single quest: bring Dung Bombs. You should avoid fighting more than 1 monster at the same time. Also, monsters have less HP than their single-monster-quest cousins, but they still have more HP combined. 1 Lagiacrus has 100% HP, 2 Lagia each have about 60% of that HP, so you will spend a little bit more time on 2 then on 1.
Also, avoid using too much materials and tools on the first monster. If you do, you might run out of Potions and stuff for the second monster. Try to use at the most 50% of your materials on the first monster. That's basically it. BRING DUNG BOMBS. NEVER LEAVE WITHOUT THEM.
The granny in the city occasionally sells Dung and on other occasions she sells Bomb Casings.
Basically, SA's don't need any specific armor skills, simply because it has everything. You don't need ESP because of the Sword Mode. You don't need Focus because you can simply reload the Phial. Simply stick to the standard skills like Sharpness +1, Earplugs and Evasion skills.
I used Jaggi Armor and later Volvidon Armor at Low Rank for my Switchaxe. Once you reach High Rank I switched to Rath Soul Armor and Volvidon S. You don't really need a lot of armor sets in Low and High Rank, just upgrade your armor with Armor Spheres as far as possible. Capcom really lowered the difficulty of High and Low Rank, which is a good thing imo.
G-Rank is a different story. You really won't make it far in G-Rank with just High Rank armor.
Helios Z with Helios X Coil is a great way to start G-Rank. HG Earplugs, Sharpness +1 and plenty of slots to gem in basically any desired 3rd skill with a good talisman.
After that, you have a luxury problem, because nearly all G-Rank armors are useful for a SA-user.
For Hammers, the story is basically the same. A Hammer can easily do its job (hit hard, kill fast) without any skills. However, the Hammer is prone to running out of Stamina because you want to be charging when your not hitting. Also, you are 100% reliant on Rolls. No blocking, no sidestepping, no awesome DS-Demon dodging. Improving Dodge skills is recommended. Finally, any offensive skill is good for a powerball like the Hammer, but it doesn't need Sharpness skills as badly as other weapons as it has ESP with the SuperPound and doesn't it very often (so no Razor Sharp or Speed Sharpener needed).
Hammer Specific Skills: Stam Drain, KO, FastCharge, Stamina, Evade Dist Up
Barioth Armor is good at low Rank, while Lagia Armor is more offensive.
For High Rank Armors, Giggi U provides Focus and Stamina Thief for quickly exhausting monsters. Barioth U provides a nice mix of offense and defense with Attack Up and Evade Dist Up. Diablos U is THE Hammer Set with KO, Stam Drain and Hearing. Agnaktor S is also interesting, as is the Yamato (Jhen Mohran) Armor.
G-Rank Armor are once again plentiful, with Helios Z + Helios X Coil as a great set. Ludroth X is also useful. Barioth Z now also provides Stam Recovery, making it an even better option. Narga Z is also worthy of mention with FastCharge, Stam Recovery and Evasion. Diablo Z lost Hearing but has Tenderizer instead, granting more power when attacking a monster's weakspot (usually, the head is pretty weak). Zinogre Z is also interesting.
If you are having trouble with small monster ruining your game, consider giving your Shaka's (Cha-Cha and Kayamba) masks that focus on attacking small Monsters, such as the Grill Mask, the Lamp Mask, the Whetstone Mask and the Gag Gargwa Mask. Also, the Flame Aura Skill will cause monsters to treat you as if you were carrying a Torch: Jaggi, Baggi, Giggi, Wroggi and Melynxes will be afraid of you, but Bnahabra will suddenly find you very attractive...
Also, giving Cha-Cha or Kayamba the Stink Mask will allow you to signal them. When signaled, they will throw a Dung Bomb at a Large Monster in the area. It has a short cooldown that decreases with Mastery, but it's definitely useful.