many fly tiers avoid tying para on hooks smaller than size 18 because they have thick fingers or or find this to difficult.
bellow you can find an easy way to tie small CDC parachute:
olive emerger
hook: Daiichi D1130 #20
thread: 17/0 UniThread
body: peacock olive quill
tail:cream fibers
hackle: olive CDC barbs
fix the cdc barbs with one turn of thread
fix the polypropylene fibers on the cdc barbs
fix the cdc barbs and polypropylene in X method
make 3 turns of thread on the base of the hackle to spread and fix finally the cdc barbs
trim the polypropylene
trim the cdc barbs
cheers

Lucian