I do the same method as Timbo when stringing with the push pull style. When you hand is on t he top limb I lock out my arm so the tip can’t move but I put the pressure against the heel of my hand. The force I apply is pulling the handle like you are doing a dumbbell row at the gym. Keep you elbow against your ribs and use your last and back to draw your arm back. This way you use your large muscles to bend the bow to get the string on. If you are actively pushing with the hand on the limb you are relying on your tricep to push the bow into a bend. And your tricep is far weaker than your lats and back. I’m 5’9” 160# and hand used this method on bows up to 100# @30” with my main shooter in he 65-75# at 27” area. That 100#er is a PITA to string like that but is doable. Once you get the feel for it down. Up to 50# should be holds play.
If you need a little weight training to build the strength to string heavier bows, then bent over dumbbell rows are perfect as they mimick the motion closely.
BTW, using this method to string a bow for tillering. For me it seems like whatever brace height you can get it to is the brace it is ready to tiller at. Essentially, if you can only manage to push pull it to a 1” brace, then tiller from a 1” brace until you an brace it a bit further to let’s say a 4-5”. This should get you to about 7-8” shy of your intended draw length at the weight you want. Then you can tiller out until a few inches shy of full draw and you should have no problem reaching full brace and fine tuning the tiller. Hopefully that makes some sort of sense.
Kyle