I have Voodoo Tactical gun bags for my guns in 42" (M4's and carbine sized rifles) and 46" (for M14's, FAL, M60 etc... that wont go in the 42" bag) and I hope to have a 37" MP5 bag next week.
For all my other stuff that you need for airsoft, (which is a lot) water, tools, snacks, bb's, propane cylinders, kleenex, blast belt, boonie hat and anything else that might be needed I have a US Army Woodland MCCEB (Mounted Crewman Compartmented Equipment Bag) which was for M1 tank or armoured vehicle crewman to keep their gear and strap it to the tank. It has three huge compartments for gear (the bottom one is for a sleeping bag and tent) and two or three smaller compartments. It's just a soft bag, no metal reinforcements inside so it's great for the trip into the field. I think I got it off eBay for like $30-35. They come up now and again.
I use the tupperware containers idea when I am camping, they make great wash bins for after supper dishes.
Level 2 Bolt Action Sniper Certified - Night Ops
Option B Stayner / Killworthy