is there any premium vechicle that can boost grind?
Are you looking for air or ground?
The USSR has a lot of good premiums. If you are looking for ground then you have 3 tanks and a sqaud vehicle at br 10 that are all great to play, Along with the su-25K at 10.3 for cas.
For air you can use the su-25k but i wouldnt recommend it. The Su-11, or Mig-21S would be a good way to grind through it. The mig 23 is a good plane too but top tier is a bit crazy atm and think you would enjoy the su-11 or mig-21s for the grind.
T-34-57 1943 for USSR, very good and skilfull vehicle.
any premium howitzer like the Brummbaar for Germany.
For air you have wayyyy too many options, all of which OP for USSR.
Germany is more of a tricky one, should probably go for the heavy gun ones.
looking for ground battles
Tiger 2H SLA for Germany, it’s not overtly different to what you’ve been playing and close enough to your Tiger 1 in BR progression for you to have a lineup in a quick amount of time.
T-34-100 or IS-6 for USSR.
Safe options based on what vehicles you’ve played thus far.
From what I’ve bought and played, I’d say go for these premium tanks: the US T29, FR Somua SM, USSR T-55AM1, and JP Type 90 (Fuji). They’re all really strong for their BR and they work great with other tanks you can buy with GE or research. They’re easy to pick up and are tons of fun to play.