sometimes spending an hour or two on a sound is necessary, no matter how tedious.
Quoted for importance. This is so true, you have to be meticulous about every aspect of a track, there is no lazy mans method that acheives good results. The quality of beats comes out the more time you spend on them. But you also have to be aware that sometimes spending too much time on a mixdown or mastering can be counterproductive, it is a good idea to take a break every couple of hours because the ears can become fatigued, and what sounds good right then might sound bad after coming back to it a few hours or a day later.
Mixing and mastering really is one of the more advanced aspects of production, it takes well trained ears, an ability to use the mixing and mastering tools effectively(compression/eq/delays/reverb/distortion etc). From personal experience it took me a very long time to get to grips with these ideas, a lot of trial and error, and a lot of reading, eventually I started to understand but still Im no expert on the subject.
Mixing and mastering are 2 different disciplines, mixing is done first, getting every instrument to sit in its place in the track, without being too out front or too far back in the mix, the panning must be right, not too far left or right, sounds should be panned to play off of one another in the stereo field, you can add stereo delays for some good fx, reverb to add some air to the drums or strings or other orchestral sounds that would sound dry or unnatural otherwise. There are some general "rules" or guidelines for various sounds, for example snares and low freq sounds are centered in the stereo field. Applying some light reverb to drums can be very effective, especially on snares and also on hi hats. Not so much on kicks but hey you are the artist, create the sound you want to create, experiment, mess around, be creative with the tools, dont take any rule to be strict and unbreakable. You also need a good quality monitoring source, be it studio monitor speakers or studio monitor headphones, Id suggest moreso speakers because you can then feel the low frequencies. There really is no point at all trying to mix or master on speaker systems that are not designed for the job, studio monitors have a flat frequency response meaning that they reproduce all the frequencies equally with no holes in the frequency range that can fool you into mixing a track wrong, trying to make up for a speakers lack of freq range, only to play the same track on a different system and it all coming out distorted or sounding wrong.
Just a few pointers trying to help you out. Im not trying to make it sound complicated, it is complicated, and thats why you have specialist mixing engineers, and seperate specialist mastering engineers. Sound engineering is very much a science, not to be taken lightly. But with a bit of understanding of the basics you really can make your tracks sound a lot more polished, and with a good understanding you can make you beats sound professional.
Also if you have to use headphones for mastering take a while to listen to finished professionally mixed tracks on the headphones to accustom your ears to hear how a track should sound when finished in those headphones, then just try to replicate it. Not easy at first but once your ears get sensitive to the subtleties it becomes easier.