Pop it down to your friendly local garage and ask them if they'd mind popping a great gun with stiff flexi extension on it. Mine does and it's worth the beer for the mechanic.
It's worth being a little careful with a big grease gun on the propshaft bearings, they are needle rollers and a high pressure gun can easily damage the bearings. Unlike the stub axles, the needle rollers on the propshaft should have a very long life with very little lubrication.
