I use a water based stain an just rub on as many coats as gives me the look I want,normaly three coats.
I seal with shellac sanding sealer,but don't sand between coats,also three.
The sealer can also be used as a water proof if you know your going to be hunting in the rain.
I think it lasts longer than most of the stuff your going to buy and if you have it on hand anyway,,,,,,,
I don't use dip tubes for anything.
If I want to cap an crest,I just use a brush and masking tape for the cap,and a home made cresting machine made from an old sewing machine motor.
You can make it as hard or as easy as you like,,,I prefer easy.
Cheers.