I spent 7 years, going thruogh my dads shop, as there was THAT MUCH stuff...
First and foremost:
1) Craigslist is a useful tool. Give away any toxic substances on craigslist. Free. Part of the issue with taking these chemicals to 'official' locations is your often limited on quanity. And if you happen to say 'too much' could open an ugly can of worms as many municipalities dont want their residents to have gallons of highly toxic/explosive stuff on hand.
Best to let CL take it. Over 7 years, I gave away over 1,000 gallons of paints and other stuff.
2) Becareful with craigslist, and do your homework on anything you decide to sell on CL. Be aware that there are A LOT of shady, and otherwise 'not good people' on CL. In 7 years of selling tools and equipment on CL, I only had to call the police once.
3) Before selling on CL make sure the building is 100% secure, incase anyone decides to 'come back' If your going to sell from the garage, use drop cloths or blankets to hide stuff... People are wierd. Its up to you to know the current retail, wholesale, and used market prices of everything your selling.
4) Clean up whatever you plan to sell, youll get more money for it.
5) You can donate a lot. Many school districts will take it, you may even be able to wiggle your way into a school tax deduction. Due to time constraints, when I moved I didnt bother with the tax deduction, but did donate well over 3,000 board feet of top quality lumber to the local schools.
6) If your going the dumpster route, try to find a local outfit that rents dumpsters. We went thru 7 20 yard dumpsters in 8 weeks. @ $300 per dumpster - paid in cash.
7) If you decide to give stuff away on craigslist make sure you list it accordingly. For instance, if it cant fit into a car/minivan make sure you point that out. Also, leave a phone number, email takes too long. Be prepared to receive tens, if not hundreds of phone calls. And about 40% will want you to 'hold it' for them. Dont hold it.. The idea is to get rid of it.
8) dont tell people anything about anything. The less people know about your situation the better.
9) garage sales and estate sales are a waste of your time and money. People visiting such sales want a $500 tool for $20. and if you go with any of those estate sales people that manage those sales, their people generally have not a clue as to what anything is worth. For instance last week end I picked up a box for of hand tools, worth around $500, for $5. because the cash out lady had no clue.
10) with dad still around, gives you a very unique oppertunity to learn, make sure you make use of that oppertunity and gather as much information as you can
Last note on chemicals, due to the EPA the rules and guide lines on the use of chemicals for different applications has changed significantly since the 1990's. Donating chemicals, old paints ect to the local schools, sounds great on paper, but can lead to an epic nightmare. First off, esp with the autmotive end of it, many of those solvents and paints, require PPE, and many schools wont want to deal with the possible liability issues... second problem, is if you have a lot of this on hand, the school board WILL inform such people as the building inspector... or worse the fire marshal and the police.... All of which leads to huge head aches, wasted time, and money.
disposing large quanities of chemicals is EXPENSIVE. Let someone on craigslist deal with it.
The right auction/auctioneer will get rid of all of it at once, and you'll get a check.
Make sure they advertise well (do your homework on auctioneer) and you advertise the auction too on CL, boards, wherever.
Auctions are great for people that need to liquidate assets fast, but realize you will only receive pennies on the dollar for stuff... the auctioneer takes a cut, and the stuff that you sell, will go cheap. It was an option I explored in the beginning til I found out that, a 3 box tool chest, loaded to the hilt with S&K, snap on, mac, and craftsman, would go for less than $1,000.
One of my dads good friends took me to a couple tool auctions, and hundreds of thousands of dollars worth of tools were going for 10-15 cents on the dollar ON THE HIGH END... screw that.