Is there any tips to reuse the wasted tooth brushes in a useful and interesting way?
I use old toothbrushes for cleaning multiple surfaces in multiple ways.
For grout: I drill a small hole in the center of the head, push a small bolt through, add nut, tighten, cut off the toothbrush handle and install it as a bit into my drill. Instant power scrubber. You can do the same with a larger scrub brush.
For cleaning small parts or jewelry: Apply appropriate cleaner to toothbrush and scrub away. Much easier cleaning tool than a sponge or scrub pad.
You can use a toothbrush and elbow grease to clean all types of surfaces. Here are some other uses:
Toothbrushes are better at cleaning inside glasses (for drinking from) than the average dish brush because the dish brushes are too large to fit inside small glasses. You can use toothbrushes to brush caked-on dirt and mud off of your shoes.
You can try using a toothbrush to remove pilling from sweaters. You can try using it to apply facepaint or makeup at your own risk.
The uses of toothbrush is as follow:
- To dye hair near forehead without smudging.
- To clean stainless steal taps.
- To remove dust from wooden furniture specialy from that areas where we can't reach or the design of furniture does not allow us to clean directly.
- To remove dead skin cells from your lips.
- For painting.
Your question mentions "spare" toothbrushes, so I'll add this suggestion. Toothbrush sanitizers are becoming increasingly popular, especially when in close proximity to a toilet (Google for details). Rather than, buy another gizmo, I have 7 toothbrushes, one for each day of the week. At end of the week I put them through the dishwasher. Toothbrush sanitation solved!
One way an old toothbrush can be used is to clean air conditioner filters. Air conditioner filters need to be cleaned regularly and a toothbrush can be an effective way to do it.
One way to do it is described in an article on Family Handyman:
After removing the filter from your air conditioning unit, you are going to want to rinse it under warm water. This will help to get rid of the initial filth on the filter. Take a spray bottle and fill it with warm water and either some soap or dish detergent. Spray the grimy spots on your filter with the bottle, then use a toothbrush to scrub off the grime.