If you enjoy woodworking, gluing wood together is an essential job, for almost all woodworking. It sounds like and easy task, but anyone who has done even moderate woodworking can tell you, gluing can be some of the most frustrating tasks you can do. The reason for this is that if it is not done correctly, for a number of things, you can end up with MUCH more work to do than you planned.
I know this from experience, and probably most experienced woodworkers can vouch for similar "learning lessons"
There are many different kinds of glues for all sorts of different woodworking applications. I seldom stray too far from what works best for me, which are polyurethane glues, (usually Titebond Original, II, or III) , more recently, Hide Glues, both pre-made and from scratch glue made for hide chips, and the ever stand-by glues, 5 minute epoxy and Cyanoacrylate glues (from Starbond) for many specialty applications.
Of coarse the first step is applying these glues and the polyurethane glues are the ones that often get the highest volume of use and the ones that can be the problematic, for a number of reasons. Many of these glues dry nearly clear, so if you get glue on areas that you don't notice outright, they can create no end of problems, to the point you end up re-sanding a project are it has been already finished once. finding glue blotches underneath your finishing is very disheartening.
In terms of applying these glues, what you kind of appliance you spread them on with can help determine how well the glue goes on how messy or NOT messy it works.
Below are most of the kinds of "glue applicators" I use, besides my finger, but I only resort to using a finger when it is one small section, otherwise I can be risking getting glue fingerprints on other parts of the wood.
The roller and the smaller paint brushes that are "trimmed" are all from dollar store stocks, as are the silicone basting brushes. In recent months I also discovered the silicon spatula heads (the handles were pulled off and discarded) which were also found at a local dollar store.
Also in the picture are some sort of plastic lid from a food container, which works great if you don't happen to have an old hotel room card, and finally an old standby for me, a cut-off or arborite or plastic laminate, I still use from time to time for very large surface in spreading glue, such as the picture below.
Once you put glue on, you need to get excess of it off, either right away when it is wet, sometimes about 20 minutes later when it is sem-dry, or 12 to 24 hours later when it is dry. For all of these, I normally use that 3 sided carbide scraper you see in the picture below, which is available from Bahco Scraper, available from the Woodworkweb Amazon Store
The other tool next to it is one that uses Razer or Razor blades, (however you like to spell it) I use the scraper for handle for things like smooth glass and steel as in table saw deck steel, but the raw blade, that is only sharp on one side works great for scraping corners with squeeze out glue ... or even if you find a drop or glue that somehow fell in the middle or the board you are gluing up, the razor blade works great for just scraping a small area.
The closest I could find on Amazon, (and now in the (Woodworkweb Amazon Store) is this set of tools that might be even better with different tools to choose from.
