Acrylic is easier to apply than urethane. It's benefit is it is not chemical resistant so can be removed if needed. If you need chemical resistance choose the urethane or epoxy. Acrylic comes with the UV tracer the same as most other conformal coatings. Check and make sure the UV tracer is in there so you can verify the coating easily.
Degreasing is critical, Tech Spray and others have electronic compatible degreasers. Check the specifications of your parts and make sure what you use is compatible. No LCD I'm aware if can take this unless it's s specialty type.
Masking the board is critical I recommend masking tape or if you can get it humiseal tape http://www.humiseal.com/
they also make a variety of coatings none of which are available in small quantities.
You can mask off plug in parts with the masking tape and just leave it on. It will allow you to remove it later to replace the part but you'll have a good hermetic seal otherwise. For far more robustness build the board with all soldered in parts.
Connectors are difficult because the conformal coating can and usually will wick up the bottom enough to interfere with connections. You'll need a steady hand an xacto knife to cut masking tape to fit. I've not found anything that works well and is cost effective. If you can afford it or have some electronic grade RTV it works well, the auto/hardware store stuff gives of acetic acid vapor and is not suitable.
Any component that is water sensitive such as LCD's come with their own problems. Since ones pre-sealed against moisture are outrageously pricey you can build an enclosure just for them and seal that. It's not hard, just tedious.
If you want this to work under water even for a short time you'll want a water tight enclosure rated for the max depth plus 25 percent. Conformal coating will enhance the devices reliability even though it will be enclosed.