Enhances and Unfinished Items

I'm currently scrolling a new katara (qq) with 20% 5att 3all 20%s and 10% clean slates from the renegades events.

I had 28 renegades scrolls & 30 clean slates. One scroll worked, and 3 slates worked.

I want to finish the 3 slots and then enhance by taking advantage of Monday's shield scroll/ward sale.

Would it be possible for me to have a +4 katara no slots, enhanced x amount of times, and to then clean slate the remaining slots back?
Basically: can I clean slate an item after it has been enhanced?

Question regarding WS/shields:

 Spoiler

What's the deal? WS have dropped from 140 to ~85m in Scania. Are they now unusable? Are they only tradeable to the Admin for shield scrolls? If the later, would it be reasonable for me to wait until WS go under the ratio'ed price of sale shield scrolls, and just exchange for cheaper ones?

Thanks in advance!