I have worn extension braids (singles) with human hair for years and wouldn't have it any other way. I don't understand why your braids got frizzy after one wash: either they were badly done or your wash method involves a lot of manipulation. The other reason I think that would cause this to happen is if you straightened your hair before braiding. I think hair should be braid stretched before braids are put in or just left in its shrunken state. That way, when you wash your hair there is no shrinking that will create an accordion effect on the braids.
I don't understand braiders' excuses that they need hair to be straightened in order to braid. I mean they work on a small section at a time. If they plaited all the hair and undid a small section and parted a row of hair that they will be putting several braids in, that narrow section should be easy to manage/comb through and add hair to w/o any problem. I think stylist just don't give a fig about days beyond the moment they work on your hair. If they did, commonsense things like how your hair will react when you wash it should be factored in so they make sure not to leave clients with a problem waiting to happen by straightening the hair knowing it won't stay that way. Also the other excuse that it is necessary for hair to blend in is BS. I have the nappiest hair and I use human hair that is silky and wavy and my hair blends in just fine. Another thing braiders do that can lead to damage is using too much hair per section of your own. That may lead to the added hair yanking your own out.
If you will be doing your own braids, then I can share my regimen as it is a self-maintenance regimen and involves redoing the braids one at a time and breaks a lot of rules, but it does not cost me retention and I wash my hair twice a week without messing the braids up.
If you will not be putting the braids in yourself, or if braid extensions are new to you, you need to read this website to learn a good braid regimen:
http://www.growafrohairlong.com/braidreg.html
I don't know what you use as your moisturizer. I am not a fan of braid spray as I think it works like glue and makes hair sticky and hard to undo.
I also believe in keeping product away from your scalp or base of braids so you don't get the product collecting at the base of the braid and matting hair up. I think if you must use some moisturizer, S Curl is easier to wash off. Otherwise I say just maintain moisture from washes involving conditioners as part of the wash and baggy every night to give your hair a moisture infusion.