I and others have posted about this before. I, and I think it was Aquarius, both realised that doing Void Meditation helps with visualisation. For me, it purely was accidental. I didn't intend to improve my visualisation, so it was a happy accident that Void helped me. Bear in mind, depending on how bad it is, and other factors, it might take a while for it to work.
Ideally, you should be doing Void Meditation every day as part of your daily meditation schedule. You never know who you meet and interact with, or just pass by, who might be able to sense thoughts; thoughts are energy, and we must control our own thoughts for reasons of making certain that any enemies are not able to detect our thoughts, and also for reasons that when doing workings and meditations we must concentrate on the goal and intention which we are working on.
Of course, everyone is individual. Be that as it may, I would still recommend strongly that Void Meditation be done from the beginning, or from the very beginning, along with Aura of Protection and Aura/Soul/Chakra Cleanings.
You can do void by just focussing on a spot on the wall or ceiling or a candle flame. Probably it would be necessary to do 5 minutes, or a multiple of 9 times (more than 20 preferably), of vibrating AUM for a week or two to test it; if it is working, then stick with that, and then increase the time/multiples as necessary. If that is not enough, then add in, along with AUM, SaTaNaMa, again for a number of minutes or a multiple of 9 (again, more than 20). If that still is not enough, then also add in the Rune ISA (or a variant of it) to AUM and SaTaNaMa, again for a few minutes/a multiple of 9 more than 20. Make sure you can handle longer times/higher repetitions; if you can't concentrate, then try a bit less; if you can't handle that much energy buzz, then do less for a while and build up carefully. Be careful with ISA; it can lead to dullness and things, but it does help to slow down things, like ice creeping up onto something, slowing it down or incapacitating it; i.e. "he/she/it is on ice".
If it still is not working, then try concentrating more - train yourself. Put yourself into the mood Psycholigcally; set the scene with candlelight, music, whatever you do to relax you (not wine, etc.) and keep your concentration. Maybe you should set the mood from the start - whatever is needed to help you. Also a healthy diet is also a must, as is consistency - preferably doing the working (and all workings and meditations) consistently at the same time or times per day. Maybe you need to do it once in the morning and again later in the evening - you figure this out. Consistency is key; repetition is key. Try not to miss or skip any days.
After you think you have managed to achieve it, keep going; don't stop. In effect, do Void Meditation until you are a God/Goddess (depending on if you are Male or Female). Also remember to not begin this - or any - working/meditation when the Moon is Void of Course. It's OK to continue during a Moon Void of Course, but not begin during one.