Best way to get "waterproof"? Brand or diy?

Hi again,
I am now on a quest for an inexpensive way to get a waterproof shell. Been going to thrift stores and scored a fantastic Outdoor Research Goretex "Seatle Sombrero" virtually brand new for only 3 bucks! Love my new hat. No luck so far on a waterproof shell, although I find lots of nylon coats/jackets of one kind or another.
So... here are my questions- What's the best brand to look for a waterproof shell/liner type coat? Is it possible to get a nylon coat and spray a sealant product on it and get a better result?
Thanks all!
Oh- In my thrift store seeking I happened to find a North Face Heli Vest with the bladder and in good shape. It's up on the bay if anyone's looking for one. I don't quite get why they are so desirable, but they are priced high.
Hope it's ok to mention this here.

I have three or four rain jackets. Still trying to find one that breathes. Rain jackets are sweat boxes if temps are not so cold; if I'm hiking and it's 50F or higher, I typically wear a poncho, or no rain gear at all. Otherwise I'm sweating so much I wet out my clothes anyway and who needs that.

PU coated jackets don't breathe at all, Goretex hardly at all - pit zips are better than most of the fabrics readily available in terms of preventing my inevitable wetness.

Lately I've started using an umbrella. It works for me pretty well in a lot of places. Probably not a great idea where there is a lot of wind (Mary Poppins I am not) and definitely not for bushwackery, but it's been pretty useful overall against sun and rain.

Thanks Lori,
It happened that right before or after I posted this question that there were posts about waterproofing on the forum in other places. They mentioned the spray silicone waterproofing product "Waterguard", I have a can of it and will test it on my old no longer waterproof jacket. The product claims to let the fabric breath. We'll see. My jacket was a Colombia, but it's been washed so many times it's not even water resistant now.
I will have to look up "pit zips".
ATB

edit- got it! vents in the armpit area which zip open to vent or breath.

I'm with Lori. A good rainsuit keeps the rain out. And if you are sitting still, that's great. If you are hiking, it quickly turns into a sauna. Let's see....dripping with sweat, or dripping with rain?

I wait a bit before I ever get out my rain jacket...just because I know that I will dry quickly in my clothes, so I am willing to get a little damp.

And when I DO put it on, I slow WAY down, and try to keep my heart rate slower....so I don't sweat the thing up.

And it never works.

I sprayed a good coating of "waterguard" on my old Columbia shell last night. We'll see if it helps. I had about a half of a can left and used it all on the jacket.
Where I live is at 7,000 feet. Where I hike is at 8,000 to 9 or 10 for now. (close by) Temperatures are generally cool enough to not sweat to death or warm enough to take the jacket off and tie it to the pack in the summer. As I mentioned, I found out my shell was no longer waterproof when it rained and then hailed on me about 3 weeks ago.
ty

Found a Marmot Oracle jacket with vent pits in a Goodwill store for 5 bucks!!! Pretty good condition too. It looks like it wasn't washed to death like my Columbia shell. So, I guess I should go out in the yard and have the wife hose me down....

So, I guess I should go out in the yard and have the wife hose me down....
She'll like that! LOL

I look for jackets, or parkas, that have waterproof zippers and no flaps so there is no place for rainwater to collect. I prefer taped seams but silicone sealed seams can be effective.

I like DWR because it is the most practical and breatheable, plus DWR is renewable with McNett or Nikwax spray-on or wash-in products.

If you can purchase a DWR jacket that suits you, do it.

If not, DIY may be feasable on a suitable nylon-fabric jacket.

Here is a link to my DIY/MYOG page to fabrics and patterns for backpacking clothing and gear.