Use these screenrc commands to bind specific key sequences to commands outside of the escape sequence (normally C-a). You can bind key combos to commands this way so you don't always have to prefix commands with your escape key sequence:

# Bind Control-PageDown to 'next', Control-PageUp to 'prev'
# to navigate between windows
bindkey ^[[5;5~ prev
bindkey ^[[6;5~ next

# Bind arrow keys Control-Down to 'next', Control-Up to 'prev'
# to navigate between windows
bindkey ^[[1;5A prev
bindkey ^[[1;5B next

(The keycodes for these keys can be obtained by running cat > /dev/null and pressing the desired key combination.)