In terms of base efficiency, both for conversion and for one's CPU, PowerConverters is (unless configured otherwise) tops for turning MJ->EU and vice versa. Hell, early on, its actually more efficient to use the converters to turn power from, say, magmatic engines, into EU instead of pumping thru geothermals. In fact, that's how I handle long-distance energy teleportation of any kind: convert to MJ, send thru tesseract, grid receives boost in power, and it works especially well with high-grade solars; I've got 8 ultimate hybrid solars working now (before people start whinging, that's AFTER magmatics, combustion engines, and even 2 small-scale nuclear reactors), and I hate having cables going thru the roof of my houses, so I'm pumping their power thru a tesseract, which I intend on using to power a few mass fabricators.
However, if you're looking for a non-converted way to generate a ton of MJ to be shot everywhere via tesseract, here's -my- idea... Since you seem to already have a fair bit of MJ production going, make a pump, pair of ender tanks, and 4 redstone engines (with 2 levers), along with some crap to build a platform to place said pump on. Find an oil well, set up your pumping station, go home, and run the oil thru a refinery or two. Don't do anything with the fuel just yet, just let it refine and shoot it off into a XyCraft tank for storage. Let it fill up til about...150,000 mB of fuel, something I managed with just 4 magmatic engines in the space of a scant few hours. Then, build a few combustion engines, water them up, then fuel 'em up, attach them to your MJ energy net (which will also connect them to the refineries), and set 'em loose. This is basically the setup I've got running in my world, and I've only fully drained one oil well. I've got only two refineries, a 7x7x7 XyCraft tank made of freaking gold (because why not?) which is remaining completely full despite fueling 17 combustion engines, which alone give me 102 MJ/t. Again, I'm barely using any fuel and am running a massive surplus with just 2 refineries and one big-ass fuel tank. The beauty of this design is that its, so long as room allows, perfectly scalable. I'd probably have more engines, myself, but the way my room's set up, the liquiducts would become a truly horrendous tangle and even turning the things on would be a chore. But, when done right, combustion engines are 100% safe and produce a great amount of power per unit of fuel; I think 1 bucket of fuel yields some 600,000 MJ total from one engine. Oh! For cooling, I'm just using a small 10x4x3 XyCraft tank being fed by 8 Xychorium water blocks, again, operating at a surplus.
Fuel really isn't the big, bad monster a lotta people seem to think it is.