just wondering, since i could not find this info from the guides, how is it to clean a dirty fresnel lense especially the groves?

It is mentioned in the care and feeding of fresnels topic. I think Brainchild recommends using very small amount of soap mixed with water, brushed on with a fine soft paint brush.

Are their easier or other ways?

I would not use soap and water you have a chance of leaving a soap film on it. I would use glasses cleaner then compressed air then a maybe a final brush with a fine (Soft) paint brush.

Cleaning is covered in detail here:

http://www.lumenlab.com/forums/index.php?s...findpost&p=5918