you might be interested in the 'micronox' torch for tougher jobs, it is a nitrous oxide and butane powered portable torch that has something like a 1/32 long flame tip and it can get heat into the right places compared to a butane air torch (it runs on whipped cream and harder to get special butane cylinders.
You can actually silver braze with it.
But it will obviously destroy plastic etc.
From my experiance, you can refill the butane cylinder the vintage ones on ebay comes with, by freezing it and making some kind of ad-hock gasket out of whatever, or using a very cold funnel and well cooled butane.
Also, I found that the penetrator on the tip are not very strong when frozen, I have two of these torches that I intend to eventually repair.
They also are a bit finicky with regulation so you need to be careful moving them around, for most intents and purposes you can use a jeweled oxy/acetylene torch for the same jobs, but this solution is extremely portable. I consider it a basement tool, and I don't like bringing acetylene into the house, so it has a place for me. Very fun too. If you can get yourself on oxygen cylinders in the same form, it should work with oxygen.
For low temperature work with solder you might want to consider a soldering gun like weller ones that are sold in autoparts stores.
When I fix it I will try to do some high silver brazing with it.