Here is a video that may help you with using cam straps:
I don't always have the opportunity to wet my straps prior to placing my BP/W or BCD on the tank so I don't. I also don't stand sideways to the tank setup , I stand on the BC or BP side and reach over the tank to adjust and tighten the cam straps.
What I find really good about the video is how the guy demonstrates rocking the buckle up to lock the tail of the strap temporarily. This allows you to adjust your grip without losing tension before threading through the final slot of the buckle and clamping it down....and/or if you need to pull more webbing through the the buckle, by rocking the buckle up to temporarily lock the buckle in position you can let go of the tail of the strap with the other hand and readjust your grip for mechanical advantage, then just slightly back off pressure on the buckle and pull more strap through, rock and hold the buckle up to temporarily lock the strap again and either rinse and repeat until the strap is tight and/or use the technique to hold tension on the strap while you thread it through the final slot and cam the buckle down completely.
All this is dependent on having the cam strap properly threaded through the rest of the buckle. If you need a video resource for that let me know and I will send one to you.
-Z