Anywhere you don't get brine the meat will be grey and not pink. Inject it all over and right down to the bone. It should blow up like a ball, and look visibly swollen. Injecting it by hand and not with a pressure pump means you should inject quite close together.
Sit something on top of the ham while its in the brine so its fully submerged.
Leave the skin on as it will stop the fat rendering out, and will protect the meat in case of any unplanned temperature spikes.
If you get the temperature right it will be done in 8-9 hours.