Play with whatever is comfortable for you while grinding tech tree or playing for credits.
In my opinion, a casual or new player won't speed things up unless they play in a platoon.

In my opinion this is an automatic mission.
All you need to do is pick a comfortable tank and focus on dealing damage.
If kills come first, that's great - but damage is easier.
The bigger the alpha, the better.

Automatic mission in my opinion.
Just play whatever you like and you will complete it.
Focus on the tank you want to slap or destroy.

Self-explanatory mission: play the game, track tanks if you can with a killing shot.
If not, then try to get 4 kills.
The tank does not matter here in my opinion.

All you need to do is 4.5k damage.
Go to the heavy line and have fun.
Any tank can work.

Play with armored tank like Type 5 Heavy, Maus, IS-7 or whatever you prefer.
Higher tiers are better, in my opinion, because there is more HP available in the game.

Brawling mission. Super heavies will do: Maus, Type 5 Heavy, etc.
Just be aggressive.

Two ways:
- either play hull-down with some tank destroyers like T110E3 or Badger and don't move
- or just play whatever you want and focus on kills; it depends on you.

This mission is easier to do in higher tiers by doing damage in heavy line.
If kills come first, that's great, but I recommend going for damage.
Once again, any tank you like can work.

Blocking is easier.
Take a super heavy like Maus, Taschenratte, IS-4, Obj. 705, or whatever else, and just play the game.
The mission will come shortly.

Two options:
- either go for kills while playing normally
- or play some stupid armored tank like K-2, Defender, Maus, Taschenratte.
It's up to you.

The best tanks for this are the ones with strong armor and low HP, such as XM57.
There are some awesome tanks to do that with like Defender, K-2, T95 etc.
You just need to be lucky.

There is no secret recipe.
Either go for raw 9k damage, or try to track every tank and farm their damage.
If you can play in a platoon, have your mates track tanks while you do the damage.

Just play a super heavy tank - Taschenratte, Type 5 Heavy, Canopener, whatever you like.
Enemies will eventually hit you.
The best part is that you can do damage to the enemy and not worry about getting hit instantly.
When the enemy is down to low HP, you can bait shots on purpose by showing weak armor.
All the damage that you have done will be calculated toward the mission.
That being said: super heavy tank.

For this one you need super heavy boy!
Taschenratte would be ideal for it.