Using round-over bits

Hi folks--

Have a question for the site. I'm building a deck, and wish to use a round-over bit to trim the outer edge of the fascia board for the edge of the deck. I've purchased a set of Skil roundover bits (1/4, 3/8, & 1/2 inch, with axial bearings). I'm going to wind up with approx. 100 ft of fascia, and would like the final edge to be the 1/2" round.

I was taught that routing is done a bit at a time--I do a lot of dovetail work and Japanese notch construction--but I've never used a roundover bit.

My tendency is--as I'll be using a hand router--to use the 1/4" bit, then the 3/8" bit, and finish with the 1/2" bit.

Thus, the question: Is this the way to approach the problem? Would multiple passes introduce inconsistency in the work, or would it be better to just use a single bit (the 1/2") slowly and carefully? (This is treated lumber.) Either way, I'm going to look like a cinnamon donut when I'm finished.

Any suggestions would be appreciated! Thanks!

Steve