1976 td15c tract tensioning

i found the tensioning zerks for the track tensioning. Do I use grease in these adjusters?
With the chain slack between the front chain idler and the 1st track idler if I shoot grease in will the track tighten? Any tricks to this?
I believe I might have one zerk dinged because I'm having a hard time getting my gun tip to seal. Does anyone know where I could order one of these?

1976 td15c tract tensioning