I dedicate a new garden sprayer to some jobs (such as bleeding a brake line from the bottom Up…or filling an axle or differential w/ gear-oil..)….
….. Cut the spray-wand between the thumb-valve and the nozzle and slip some polyvinyl hose onto the wand…. and route the other end of the hose to the fill-hole. Pump up the sprayer and press the thumb-valve.
This was particularly helpful when the front axle called for 8.5 qts of 80W90…. I can see the graduations on the side of the sprayer reservoir to determine how much has been delivered.
One time use sprayers from WalMart are $8… Long-life sprayer tool for repetitive use…buy a better quality one appox $16-$20…. My gear-oil sprayer has been my friend for 15 years, used for tractors, cars, trucks, shredder/PHD gear-boxes, etc. etc. which use common 80W90.
Another sprayer delivers ATF fluids….