#1
hello

im terrible at bar's my fingers are tiny childlike and weak , any exercises that i could do to build them up apart from playing barre chords obviously i mean exercise without using a guitar

cheers
#2
exersice with a guitar is the best kind

try doing three string barres and when you get comfortable with those move up to 4,5,6 strings eventually youll be able to barre everything everywhere with all you fingers(pinkie takes a bit longer than the rest)
#3
Practice doing it. Your finger will stregnthen over time. Orr tiny dumbells...lol only joking.
Gibson Les Paul Classic
Fender Stratocaster (Mexican)
Hagstrom Ultra Swede
Music Man Axis Sport