I did that once but I used a friend's grease gun that was filled with Crisco. Once it hydrauliced the ball out I just left the barrel in the sun at an angle and the Crisco melted and flowed out saving a huge mess...According to a post/thread some time back on this forum it was pointed out that Zerk grease fittings have the same thread as most percussion nipples and that an ordinary grease gun can be used to force out powder less loadings.
Inquiring minds want to know..... ?got the ball out the old fashioned way. ...