The trick with Hail teams is you have to really work hard to balance out the weakness. You definitely need a Weather setter (NO REALLY?!) and the best (imo) is Abomasnow. If you're playing Gen 6 you also have the option of using Aurorus, however that requires getting it with it's Hidden Ability, plus it doesn't have the same diversity as Abomasnow.
So we start with Abomasnow.
You also wanted Walrein so we'll add him in there immediately.
So let's take a look at some weaknesses we should cover: Fighting, Rock, Flying, Bug, and Fire are all some pretty big weaknesses. One dual typing which would be effective in lowering two of these weaknesses is a Fighting/Psychic type. Medicham is a fun Pokemon to be used in-game and has a great diversity in the number of set it can run. Looking at the weaknesses now, Ghost, Flying, Bug, Fire, Steel and Poison, a Pokemon who can effectively be used, is a steel type. Now you are still partially weak to Fighting attacks, so you could either go for Skarmory or Aegislash (if playing Gen 6), or you can go for Heatran (if you can obtain him) which means Fire isn't a problem. Let's say you go for Skarmory.
Now you are still weak to the following types: Electric, Flying, Rock, Fire and Fighting. One of the dual typings that can handle three of these weaknesses is a Water/Ground type. My initial suggestion is Swampert. However if you prefer a far more stall biased team then Gastrodon is also an acceptable choice. Now your weaknesses are: Fighting, Flying and Fire. Sadly there is no Ghost/Rock type. However there is a Ghost/Fire type.
Now that you have the bones of a team to work with, let's talk about sets.
Abomasnow has a good variety of stats to work with, as you have Walrein and Skarmory to fill your role of walls, you can go for a Mixed Attacker.
Abomasnow @ Life Orb/Expert Belt
Trait: Snow Warning
EVs: 252 Atk / 108 SpA / 148 Spe
- Wood Hammer
- Ice Shard
Your choice of Life Orb or Expert Belt. This set gives you some STAB moves with added coverage, with the EVs taken shamelessly from Smogon.
Walrein is best classified as StallRein on Hail teams. The set is fairly straight forward so I'll just copy paste it.
Walrein @ Leftovers
Trait: Ice Body
EVs: 232 HP / 36 Def / 216 SpD / 4 Spe
Again Smogon's SDef EV spread, with moves also from Smogon, although commonly seen on StallRein. Toxic + Protect + Substitute + Leftovers + Hail = Complete and utter stall. Blizzard is in case of Taunt, and also gets STAB.
Skarmory is going to be your Defensive wall, and Hazard setter.
Skarmory @ Leftovers
EVs: 224 HP / 252 Def / 32 Spe
- Stealth Rock
- Brave Bird
Leftovers cancels out Hail damage while Roost gives you the real HP recovery. Brave Bird is an attack designed to take out any stragglers and any Taunters, while Stealth Rock and Spikes allow you to wear down your enemy much faster.
As for Medicham, on this team I'd suggest a Choice Scarf set as you lack very speedy Revenge Killers.
Medicham @ Choice Scarf
Trait: Pure Power
EVs: 252 Atk / 252 Spd / 4 HP
- Hi Jump Kick
- Psycho Cut
- Trick/Drain Punch
For your last moveslot you have two options, Drain Punch is a safer STAB, and will allow for more survivability in Hail, whereas Trick can screw over your opponent by locking them into a move such as Toxic, or Taunt. Hi Jump Kick and Psycho Cut are both STAB moves, while ThunderPunch is coverage.
You can also go for an Adamant Nature, instead of Jolly.
Since I have given Skarmory the role of hazard setting, you have no need to run Stealth Rocks on Swampert. This means you can run a Bulky Phazer set, or a Bulky Mixed Attacker. I'm leaning more towards the bulky Mixed Attacker set.
Swampert @ Life Orb
EVs: 240 HP / 160 Atk / 108 SAtk
- Hammer Arm/Stone Edge
Mixed Attacker, Physically biased with Hammer Arm or Stone Edge as your choice in the last slot, I would personally go for Stone Edge to get the EdgeQuake combo with Earthquake. Blizzard > Ice Beam to take advantage of Hail.
The last Pokemon on this team is Chandelure who can take advantage of Abomasnow's 4x weakness to fire by switching in with his Flash Fire ability. For Chandelure I'd normally suggest a Choice Scarf, but since Medicham has filled that role, we can run a different set instead.
Chandelure @ Life Orb
Ability: Flash Fire
EVs: 252 SAtk / 4 SDef / 252 Spe
- Shadow Ball
- Fire Blast
- Pain Split
- Energy Ball
Shadow Ball and Fire Blast are your two main STABs with Energy Ball as a coverage move. Pain Split can be used to restore health from Hail and LO damage. I chose to a Speedy Special Attacker over a Bulky Spread to increase the amount of HP Pain Split gives you.
Now, by no means is this a perfect team, and you may decide to go for someone else. It also depends on the game you're playing, I assumed Gen 5. Also if you decide to use this for competitive battling I would suggest getting a Spinner (A Pokemon with Rapid Spin) in there because three of your six Pokemon are weak to Stealth Rock which is a bad considering Stealth Rock is the most common entry hazard in existence.