Help, Tremolo problems. Largo Dvorak piano solo

[chopinj]

Hi , i have recently started learning Dvorak's Largo from the new world symphony. It  is the full piano solo/orchestral version. I am on at the bottom of the second page and am having trouble with the left hand tremolos in the treble clef. The trouble is that i am not use to playing tremolos especially in intervals of 5ths and 6ths. please help if you have any suggestions on how to play or practice these tremolos it would be greatly appreciated.