Oil for flow vis

I have used 'used' motor oil. Drained from my car
after 3K to 6K miles. Nice and black, and not too
thick. Started out as 10W-30.

I have also used new automatic transmission fluid.

Darker is better, but either works. Brush it on, and
make sure you don't leave bristles or other things
in the oil. Have lots of 409 and paper towels on hand
for cleanup afterwords.

I have always had trouble getting what I thought was
good oil coverage on the bottom side. Next time I
do any oil flow work, I will set the wing upside down
on stands or saw horses or some such, brush the oil
onto the bottom side, flip the wing over and plug it
in, brush on the top side, then go fly.

What 'cha checking into?

Steve Leonard
Wichita, KS