Do not be discouraged! Practice will enable fast focussing to become second nature.
The main advantage is that the lens isn't hunting focus at the moment you want to fire the shutter. It is set where you've put it. Sometimes that can be a greater confidence builder than the false confidence of autofocus. It only changes focus when you choose. Control.
Practice using likely settings and distances, beforehand. Muscle memory is very important and ease of use, means many otherwise fine pieces of equipment are never used.
Find your favourite lenses and practice with them, when sitting in front of the TV during a break at work etc. Sit at various distances and focus without using any viewfinder. Educate your hand to find the focus distance seen by your eye?
If you've just captured an image where you carefully focused through the viewfinder, and another person enters your field of interest. By merely releasing the shutter when they're the same size in the viewfinder you are using your previous picture as a focusing aid, judging subject distance by its relative size in the viewfinder.
Don't tell me it is impossible! Do it! Try and see if you can surprise yourself. The lens can accept markers, preferably glued on, with strong tactile feedback, enabling feel of the lens to be correlated to the eye.
This will differ for various lenses so be drastic and use a max of three for this exercise, probably your fastest, to freeze movement, but not necessarily the sharpest? Some lenses will not be suitable for this treatment, if they have controls that require tiny movements to cover your full shooting range, then will it be possible to use depth of field to ensure that once set, the lens need not be focussed again at all. For lenses with a large "throw" meaning that the focal ring can be twisted quite a distance then these techniques may be more useful.
Knowing the range of each lens, for specific types of photography, means that your restricting photography to an almost automatic reflex. For each specific subject matter, the lens will be restricted to a certain focal range. The marking therefore should be to enable these ranges to be found by feel in the dark, if that is associated with the subject matter.
If a subject is a distance away then the lens markers may have to be reset. Take the time before the shots start to make the likely focal distances as relevant to the markers as possible.
Try to multiply the sensory aspect of manual operation especially with lens stopped down two stops for best performance.
The markings on manual lenses may be of no use for determining range or infinity if used on say m4/3 sensor camera. Making new markings may be practical.
Do not just be satisfied with getting close to correct focus, practice to get it perfect. Use your body to find perfect focus too. If you have grasped the lens in a certain way, you may need to reposition your focus hand and that may cost more time than a pace towards or away from the subject.
When only manual focus lenses were available, photographers would burn through dozens of rolls of film per event, or use bulky 750 frame film backs, hoping for that one shot that they could sell and they managed to get it, perfectly focussed.
In this day of DSLRs and mirrorless cams, where there are no film costs, and no need to reload until one fills up a memory card, and the ability to erase pics taken, and auxillary memory in form of portable hard drives, frame rate per second is becoming very high, albeit at the same focal point. Currently, 10 frames per second are acheived. Some cams offer higher rates, designed for manual focus, at the loss of some resolution, but 5 megapixels is quite adequate for most purposes and even less is acceptable, if focus is acheived of a spectacular event.
One of the techniques, when shooting very fast cars or sports action, was to pre-focus on a specific spot and then trip the release just before the spot was reached. This allows for reaction time and the time taken to open the shutter. Trap focus is the name for that technique. At airshows, aeroplanes, fly at about the same distance from the crowds, so attempt to keep focus at that range.
Patterns are usually discernible, but always shoot, as practice frequently makes perfect focus and that unconscious perfection only comes with repetition, so get started.
It can only develop with practice and you can be happy with each step of your progress.