I would suggest the following.GPSTrimble R-10 with Access software. Also with a subscription to Trimble VRS network. It works ok in cover with the occ...

If your using the trimble R-10 you have to go into your survey style and under rover options tab to the 3rd or 4th page... you will see a box checked ...

I actually attended a class to learn how to flag wetlands the instructor told us he liked to hang the flags in hard to see areas to mess with the fiel...