There is a really good screw for Simpson tie fastening ... DSV http://www.strongtie.com/webapps/fastenerfinder/index.aspx?description=DSV&type=Hand-Drive%20Screw?source=fastenhp#
Check to see if they have the proper length for yuor application. I prefer square drive because it does not slip as easily as phillips and you can really lean into them.
If you use an extension ladder (not the A-frame) you can lean into the wall better.
BE SAFE .....