I hold (support) the sticks in my left hand and support the forestock on top of the closed fingers of that hand. I don't shoot a heavy recoiling rifle from sticks, so haven't worked on that aspect. I know you are talking about shooting from sticks in the African Veld. Sticks were invented by PH's who were distressed by the poor shooting of most of their clients. Seems many who can afford to go to Africa don't shoot as much as they should and therefore lack the requisite skill for making good offhand shots - hense sticks.
Shooting a muzzleloading rifle is very good practise for offhand shooting - it's what we do all the time - it develops good hand/eye co-ordination so one lets off the shot at the correct time. It is the very best 'practise' one can use. If you can shoot a 'real' muzzleloader accurately from the standing position, shooting a modern rifle from that postion is dirt simple.