If you're dicing with death in this manner, it's much safer to fill the container with water before you pump it up then there's only a small amount of compressed matter to explode.
Depends on the rivet - pop rivets often leak but more sophisticated items like Avdel and Cherrylock retain the mandrel and seal effectively. These are often used on a/c primary structure.
I always used jointing compound (yellow gunky stuff) - this seals and prevents corrosion, though if your rivets are correctly spaced and holes deburred you shouldn't get leaks.
When I was sticking aircraft together I used 3M EC847 to stick dissimilar materials together. Eg polyurethane strips to grp rotor blade LE and rubber gasket to Al alloy doors and panels. The solvent is MEK so you need to be careful with it.
Perhaps it's already been mentioned, but renting a square foot of high street in a large city will cost a grand a year. Bit different to working from your shed...
Started using flank drive in the early 70's - recommended by RR and Westland on their aircraft (mostly titanium fastners) never had one trash a bolt head.
Tipping out gas...
If you're going to tip out gas, have a care about where it goes - it's heavier than air and will run into drains and pits etc. A mate of mine was standing on a drain cover when the petrol vapour in the drain below exploded - lifted him 3 feet in the air...
Lakeland do a (probably silicon based) lube which is extremely slippery but not greasy http://www.lakeland.co.uk/free-'n'-easy/F/keyword/slide/product/8998
Spent many hours on the instrucibles site in the past... this one is fun:http://www.backyard-ballistics.com/ how to make a spud gun... with a range of 1000 feet...:D
Aside from melting the alloy it's a reasonably easy process - I learned how to do basic stuff in school casting inlet manifolds for hill climbers. Don't think I want to try engine blocks though...