50 For Custom steering box

[Bullerman]

Steering is stiff on my 50. Have had the car about two years. It has been like this since I have had it. It's like it doesn't have that much rebound.
I want to check the grease in the steering box but not sure how. It has the steering box screw for adjustment and one other plug on top.
Do I just pull the plug ( if I can get it out) and try and force grease in the box. Anyone tell me what I should do. It may have the original grease in it.