Bill mentions a really great product. Like a lot of things we have become fond of over the years, sometimes they just fall off the market. I have never found a glass cleaner product for washing auto windshields even close to Glass Wax. Glass Wax, formerly a Johnson Co. product was sold and the new company let it expire. I found a close substitute, ironically an Ace Hardware glass cleaner/polish.
The ceramic filled Devcon white 2-ton epoxy remains a nearly perfect product. It has strength, smoothness, little to zero shrinkage and bonds well to many materials. I use it to fill in flush windows on cabooses without any sanding by following a basic cool technique utilizing scotch tape. It sands well, and I use it for filling both resin and plastic models imperfections. I cringe when thinking about using Squadren green or 3M puttys because of how much poorer these products are for surface filling.
Like a lot of missing items, I have been unable to find Devcon white 2-ton for over 5 years now. Fortunately, Ace has a "2-ton epoxy" which is very similar, if not exactly the same as Devcon. But that is now getting harder to find. I now use Ace "waterproof epoxy" which is also really good and still broadly available. If this gets hard to find, J-B Weld epoxy works well and is found at any auto parts store. It is a dark gray.
All of the above mentioned products requires hours to cure, but as Bill mentions, the working time is quite generous.
For casting model parts I have found 2-ton epoxy to be a great material. It takes the detail as well as the polyurethanes, down to replicating the MEK shine from the original patterns. I have some N scale F-unit open cavity molds which I can cast thin shell bodies from without an inner mold. The paste thickness
allows casting a side laying the mold on its side. Rotate the mold 90 degrees and pour the roof. Stand the mold up on end and do the nose.
If a less viscous epoxy is needed, the epoxy thins really well with isopropy alcohol with no observable weakening of the cured part. Epoxy can also make small parts from a single-use mold such as modeling clay pressed over a detail. If carefully removed from the pattern a small mixture of epoxy can make great parts. This is a fine way to get into
owner-casting of hobby parts. You could go to Michael's craft stores to buy a product called "Amazing Mold Putty". This is a 50-50 mix of 2 components which is slightly less viscous than silly putty. It is stiff enough to often avoiding making a mold box. I have the Rock Island 16100 Shake N Take Athearn donor car providing the replicated shape mold non-destructively.
Over the years after several frustrating attempts to use Epoxy to attach vulnerable parts, Andy Carlson alerted me to Ace Hardware's "Two-Ton Epoxy." Over the past several years I have never has a problem with this product and used it today to attach a "Triple Valve Protective Plate" to a VGN SS boxcar and fill in the Coupler Screw holes on an underframe that I miss-drilled. Great stuff, never fails to harden, it is slow working allowing plenty of time to work. I don't use anything labeled "Fast" or "Quick" except for CA.
I highly recommend this product! Thank you Andy!