I want to make my website refine panel on the search result more user-friendly. Im dealing in realestate portal and have already implemented one but not sure if that is the best way to do it. So need your help.

I have more than 10 categories in refine section, and ongoing I can increase them. My question is:

Should the refine be auto-triggered? For example eBay have auto triggered refine, as soon as you select your results get refined, or should I add a refine button for each section of refine panel? For example if user selects option A in particular category, we show him refine button:

so that user is sure that he has selected option A and now he will get results only for that..

In eBay search format if user selects something by mistake his results will get refined and he will not understand it, Here is an example eBay search to illustrate what I mean.

If I do use an auto triggered refine – should I add loader and grey out the entire screen so that user know that something is getting updated or should I just show the refined result like eBay? Will it surprise my users?