For pumping nipple balls often use Bicycle pump with a special needle. But it does not matter if it broke or its just not there at hand: with this work well covered by a normal Bicycle nipple off a rubber tube mounted with its threaded shank in the hole of the pump.
Recommend to read
HIGH-SPEED ASYMMETRIC
The proposed control line speed model (C. F2А) asymmetric scheme designed and built in the aeromodelling club "Falcon", under the leadership of its founder and coach B. I. Shibanova,...
HACKSAW FROM SCRAP MATERIALS
As an Amateur I sometimes need a tool that is rarely or on sale, or is not satisfied by construction, (and today — and for the price). So we have to invent and produce itself, looking...