How can I read a list of filenames from a file in bash?

Use read:

while read F  ; do
        echo $F
done </tmp/filelist.txt

Alternatively use IFS to change how the shell separates your list:

OLDIFS=$IFS
IFS="
"
for F in $(cat /tmp/filelist.txt) ; do
  echo $F
done
IFS=$OLDIFS

Alternatively (as suggested by @tangens), convert the body of your loop into a separate script, then use find‘s -exec option to run if for each file found directly.