no pics, but what i do is use a 6oz soda bottle, a little bitty one. basically you put your liquid in the bottle, squeeze it until the liquid hits the rim of the bottle, and then screw on a carbonation cap. zero air in your system. blast that sucker to like 30-40psi. you want a decent amount of head space in bottle when its gassed up to propel the liquid.
then it goes bottle+ carb cap to my injection rig is which is liquid qd--> tiny piece of 1/4 tubing over both barbs<-- gas qd on the keg.
purge your rig with co2, then connect the bottle, then lastly connect to keg gas post. blam. liquid is in, nothing coming out. works for biofine/gelatine, adding more gypsum/chloride/salt/acid/hop tea/etc. when needed.