Beginner’s question 😉 Applying lubricating nipples / grease press

Moin people, I just wanted to supply the lubricating nipples with some grease in my “new” Camaro 2nd generation. I now also have Pressol’s grease press with flexible hose, but if I put it on I can’t fix it. So I need three hands to press on the adapter, hold the press and use the lever. Is that normal? Do I need a different size? Thank you for your help!