I'm just a mom but I'm pretty sure you need the hand strength with the thumb on top to smoothly connect the skills, my understanding is that wrapped thumbs on girls bars are only for front giants and similar skills...per my L8 DD and L8 DS who of course know EVERYTHING...
It generally takes a long time to connect all those skills smoothly - the girls I saw connect them easily were the tiny thin ones who swing really well on bars - DD took almost her whole year of old L5 to smoothly connect a whole bars routine but less than a year later had a great and connected L7 bars routine - so for her I know it was the difference between muscling through the skills and learning the rhythm of the connections - plus strength and lots of practice. Now she's back to muscling through L8 bars skills after puberty changed her body proportions.
I think repeated kips and repeated kips to casts without the rest of the skills have been a huge part of bars for her team (of course now its kip cast handstands or 10 kips in a row, or kip castHS pirouette, etc) so that the connections eventually come naturally...
give it time....its hard stuff you're trying to do - even at L4!