Start front squatting. At my last comp, I loaded a PR stone of 310lb at 195 body weight, I attribute that to training front squat with wendlers 531. Last comp as I tore my shoulder on the very first bloody event!
Any gym move where you are front loaded with weight will help (front SQ, zerchers)
IMO (everyone is different) front squat and incline press (log or axle) are more beneficial to a strongman than back squat and flat bench.
It is tricky to train for stones without stones. In a pinch you can shove a bar through some 45's (bumpers) and practice the pick.
If you can get a keg and fill it, you can train the loading portion. I use to see them on craigslist a ton.
Get tacky!! Chances are you can borrow some off of a fellow competitor. Spread some on your inner forearm, palms and put a big dab on the back of your hand incase you need to reapply if it is for reps.
This is how I load a stone (everyone is different)
Straddle the stone, insteps inline with the thickest part of the stone.
Slide your arms directly down over the stone (straight arms, vertical, don't try to cradle the stone)
Rock the stone side to side to get your fingers under a little
Squeeze and stiff leg deadlift the stone up and sit back as soon as the stone passes your knees, buckle your knees in underneath to support the stone.
Lap your arms over the top of the stone and move your feet in slightly.
Hunch over, stick your chin on the stone and glue it to your upper chest!! DO NOT let it slip down when you stand!
Throw your hips forward and roll the stone up as you arch your back, use your belly as a shelf! stick it way out!
Once high enough lunge forward and chuck it over the bar or load it, whichever the event is.
Being new to stones the pick will seem hard. Keep pulling!! it may feel like it is glued to the floor but it will eventually move, just like a stubborn deadlift.