Stephen Welsh asks:
Smaller flys (16 - .) blend, tie in clump and trim to shape.
Larger flys (14 - Beyond) tie in a clump (not necessarily blended) and
leave.

Is that about right?

Two minor details. First, for larger flies, feel free to trim, should you wish
a neater effect. I have no clue whether the fish care.
Second, for smaller flies, a couple extra procedures to play with: a) Bind a
sparser clump across hook shank, bind down with a couple cross wraps like a
spinner wing.
Pull both sides upward and take no more than two wraps parachute-wise around
base of clump.Gives the neatest fan-wing on small flies, with no bulky tie-down
point behind wing. b) for Downwings, take a sparser clump of unblended hair,
bind down with tips to rear with a couple wraps of thread, then, pull back
butts of hair which point forward. Pull them back in two parts, one clump to
either side of tip hairs, bind down with a couple more wraps to form a nice
down wing, clip at end of wing to shape.
Now, practice away, and fish with the flies.
You will enjoy the ease with which they stay functional, fish after fish.
Tom