I've seen a few -8's that used a computer fan mounted in the glareshield for a defroster. The only time I needed one was last summer when I departed OSH in a drizzly rain. The window fogged up while taxiing, and I used a paper towel to keep it clear. As a bonus I wound up with a really clean windscreen

Once underway there was no need to keep wiping as cabin airflow kept it clear. YMMV