I am covering the wings on my LT-40, and was wondering if anyone had any tips. As you know, this is a big wing and is tough to manuever and handle when trying to do this and keep wrinkles to a minimum. Any help is appreciated.

How To Cover check this link
http://www.rcuniverse.com/reviews.ph...ew&reviewid=67
or check here for good tips
http://www.airfieldmodels.com/model_....htm#Finishing

I didn't look at the links the other person posted for you but i'll give you a tip.
1.If you haven't started yet then ask questions and ask a whole lot.
Lot of Guys here did a lot of wing covering.
When you do start and things just don't seem right then STOP!!
Come back here and tell us what the problem is.
It may cost a bit more but you can't beat frabic for covering.
Not to long ago I recovered a wing with duct tape,masking tape then covered the entire wing with clear packing tape.
I assume that you have the proper heat iron and padding.
So all you need is to go slow and you'll have a nice covering.

Well, up to this point, I have done the Ailerons, Rudder, Elevator and Hatch, and all have come out surpirsingly nice. I am very proud of it. The wings is another animal. One thing I have found is that if there are undulations in the material, you will see them, and once they are covered , you're stuck with the,. Overall, it has not been too bad. I have not done the tops of the wings yet, but so far I am happy..

One thing, I did not "stretch" the covering over the wing tips, as I have been suggested to do, I don't know if I can do this safely as I have no one to help me hold the wing, pull the covering, hold the heat gun. I just did it with my iron and it seemed to come out ok.

OK so your almost there.
If your looking that good and happy I wouldn't do the wing yourself.
It looks like your striving for perfection and nothing wrong with that because your work will show up when your finished.
Get some help and you'll have control of the covering and tighter skin.
Maybe some of the Guys here who work a lot with the same material will shed some more info for you
To bad they don't make the wing covering like socks that you can slip on then heat and shrink it.
Keep `us posted

If there's no one to help you, you can put a blanket or pillow over the wing with some weights (maybe some books?) to hold the wing for you while you stretch the covering.