PLEASE DO NOT USE TAMPONS!!!
Tampons are unhealthy because they encourage growth of unhealthy bacteria, they prevent vaginal cleaning by keeping this bacteria within your vagina, and damage vaginal walls (particularly when not menstruating, as it states on most boxes, as with no flow they'll absorb more flow thus causing more drying and ulceration/splitting as a result- this increases TSS risks by at least 33%) - as such they are a well-known common CAUSE of vaginal infections.
Even if you're menstruating you should NEVER use tampons during an infection or with unusual discharge as the bacteria responsible for TSS may be more likely to be present within your vagina so significantly heightening risks. Doesn't matter if you're changing every 2 hours - the idea that TSS only occurs after 8 hours is total and utter myth, it can occur within 2 hours, so there is still significant risk.
If you want a mess-free way of inserting the yoghurt the best way is to freeze the yoghurt into ice cube trays (acidophilus can easily withstand freezing) which also makes them extra soothing if experiencing burning or itching. Some yoghurt will also come out over your vulva.
To avoid mess use pads - commercial pads like Always should be avoided as chemicals will irritate and synthetics/plastics will prevent air flow making you uncomfortable and giving yeast the perfect breeding ground. Use cloth pads like Lunapads if you can, or at least cotton pads like Cottons which are hypo-allergenic and allow for more air flow.
Or of course use other methods; garlic, tea tree oil, hydrogen peroxide rinse, gentian violet, cranberry/blueberry juice, acidophilus tablets, boric acid, or any over-the-counter treatment.