Head gasket in a bottle fix?

I'm wondering about peoples experience with head gasket in a bottle fixes. My 2nd gen prius has 270k miles on it and has the worst coolant smell coming from the exhaust. But I dont notice any milkshake in the oil and I did a leakdown at 100PSI the numbers looked pretty good from 4% to 10%, no bubbles under the rad cap, coolant level doesn't seem to change at all. The engine already burns quite a bit of oil, about a quart every 1000 miles. It's done this since 200k. I have a line on a junkyard motor but I wonder if I should just pour in a bottle of the HG stuff and see how long it goes. Mostly because I am very lazy and a motor swap is a lot of work to me, especially in the winter. What do you think?

Think the stuff I have had decent luck with is called K seal. There are a couple others that people here have said work well.  The K seal you just put in with the antifreeze. It has hot to the pint that I just add a bottle to my cars every two years when I change the coolant. I have never had any heater core issues with it. 

The previous owner of a Camry my wife used to own had used a head gasket in a bottle fix. It lasted just long enough for us not to realize something was very wrong, and failed completely about a month after buying it.

Blue Devil.  Works with water only, though-no coolant.  And about $60 a bottle.  But it works. 

In the early 2000s Subaru had a recall which involved dumping a bottle of stop leak in the coolant to prevent head gasket leaks.

My 2004 Outback had an external HG leak when I bought it (about 1gallon/week). I dumped a bottle of the Subaru branded stop leak (aparrently it was a relabeled Holt's product) and drove it for 30k miles with no adverse effects that I could tell. 

Eventually it started overheating and I changed the HGs. I did not notice any gunk or blockages in the cooling system at this time. 

I also used the Subaru stop leak on two different EJ25…3? (2.5 SOHC) motors which sprung coolant leaks at around 200k miles.  Both were still running fine when I sold the vehicles ~40-50k miles later.  One of them I still see driving around town despite cavernous rust holes everywhere.

Those were external leaks that simply resulted in gradual coolant loss, though.  No overheating, no coolant in the cylinder, etc.  I doubt very much that stuff would have helped at all with a more severe leak

Very recent thread on blue devil. Yes, it does work (according to my admittedly small scientific sample size). 

https://grassrootsmotorsports.com/forum/grm/blue-devil-im-a-believer/145168/page1/

I have used Blue Devil successfully before in a E250. Follow the directions. It will not work with any coolant in the system. 

So basically I tried a bottle of this garbage and not only did it not fix my HG, it partially blocked up my heater core. I have a replacement engine waiting to go in, how can I flush all remnants of this stuff out to make sure I don't block the cooling passageways on the new engine?

'this garbage' meaning blue devil or some other garbage?