Soda blasting takes fairly specialized equipment and technique so you will likely need to hire an outfit to do this. I keep my boat at home and I used a commercial blaster with walnut shell media. It worked great, took about 4 hours and cost about $500. If the yard does the soda blasting, sanding and painting, you are looking at big bucks. For your boat, probably in the neighborhood of $5000 minimum.
As for barrier coat, if you already have one then you should not need to replace it. If not, most yards will recommend adding one if you strip all the way down to gelcoat anyway.
To answer your question, yes, this is a good thing to do. In the future, use only multiseason ablative paint for the bottom to prevent the buildup of paint. It seems very common for owners to cheap out and use a hard paint which will eventually result in this thick buildup of flaking paint. Hard paint is ok in some areas but in the NE where you are only in the water part time, multi season ablative, I feel, is the best paint to use.
BTW, I applied the necessary coats of Interlux 2000, one coat of red ablative bottom paint and 2 coats of Interlux Micron Extra shark white. I added a third coat on the high wear areas. I now only apply 1 thin coat of Micron Extra every spring with and extra coat on the wear areas. My boat stays in the water 7 months with one bottom scrubbing in the beginning of August.
