I prefer the west system epoxy resin. I keep both 205 (fast) and 206 (slow) hardeners around the shop depending what I am working on and the temperature I am working in. I like West because it is a very good product and you can buy those conveniant pumps that meter out the resin and hardener in the exact ratio quantities you need. Though West is probably the most expensive Epoxy-Resin you can buy I have never had a failure and when dealing with 125+ gallons of liquid I don't ever want a failure.
For the cloth I just buy plain 6 ounce Hexcel cloth. Most boating supply stores carry both the cloth and the epoxy resin. While I don't mind buying the epoxy resin at a pricey boat store because you have to factor in shipping from an on-line place,
That is the best price I have found on the cloth yet and I tend to buy it 50 yards at a time, shipping is reasonable, and they will sell down to 5 or 10 yard quanties, if you call them they might sell less.
I am sure you know you can just cut the cloth with a nice pair of shears, my wife got pissed off at me after using her nice quilting shears so she finally bought me my own pair so I wouldn't dull hers and have to resharpen them.
I also use the quilting rotary cutters for cutting the cloth, when using scissors I hate dealing with cloth that bunches, with the rotary cutter I just lay the cloth out on my table and can lay a straight edge on it and rotary cut the whole thing quickly. Jo-Anns sells the rotary cutters and the replacement blades are cheap enough. Again my wife gave me one after I kept taking hers. The table will get scratched up and they make cutting boards specifically for the rotary cutters but again I have to borrow my wifes if I want to use it, I just cut on my work-shop table and don't care about scratches.
For the actual application of the epoxy-resin I use the rubber squeegees that you buy for doing automotive body work. After the epoxy cures on them you just flex them and the epoxy breaks right off, I have had the same set for 5 years. I also buy kitchen rubber spatulas that I can shape for the hard-to-work corners and such. Once the cloth is applied and the wetting coat of epoxy is applied with the squeegees I will switch over to the cheap 1" foam paint rollers for spreading the filler layers of epoxy-resin and just throw those away. Make sure you take them off the roller before they cure or else you will be buying new roller handles as well.
When working in the boxes, mind the pooling of excess resin in the bottom, if it gets too thick it could crack during curing, I have had enough cracks in my cured epoxy that I had to grind out and restart that I know what I don't want to do. It is easier to add more epoxy than to take away epoxy if you have too much.
I have an entire write up on the building of a fiber-glass aquarium, it is posted on a fish-site. If you go to http://www.cichlid-forum.com
and if you follow the Library link on the left and then scroll down and find the DIY section, there are a few articles on building the plywood aquariums. Just ignore the parts about the acrylic front/sides and build a solid box. I tend to use Stainless Steel screws rather than brass, I don't care about the color of my exposed screw heads and prefer the square-drive screws.
For the baffolds I am just going to use the same 7/8" plywood, cut some 1" holes near the bottom (break out the bottom edge with the band saw), epoxy them (don't think they need cloth since they don't need to be strong) and glue/screw them into place inside the tank. That way the liquid cannot get any linear movement built up.
For the top of the oil and water tanks I am just going to cut the top out, glass it up and then use liquid nails to glue and screw it on, then fiber glass the outside corners, since the top will never be immersed I think this will be enough to prevent spillage.
I know nothing about the fleece applications.
I will document the 80-gallon oil tank and post it on here and/or my other bus-building web site as I go.
If you are going to have the tank exposed inside the bus and use for a bench seat or something, you might want to consider using the oak or maple plywood. I tend to use this even if it is not exposed because it is usually better quality than the regualr construction plywood. The oil tank will be built from this and then a separate insulated box will be built around it so no one can touch the inner tank and risk burning themselves.