How do I make new small crates look like old wore ones?

I have use the vinegar and steel wool stain solution, to apply to new PT wood to replace rotted PT boards making a better match to existing decking with great success. If you like gray tones this may be your answer.

http://www.adomesticlife.com/natural-wood-staining/

https://www.doityourself.com/stry/how-to-age-wood-for-a-rustic-look

1. I've tried a product by Rust-Oleum called Weathered Wood Accelerator - you only need a little and it works quickly! Here's a link to the info: https://www.rustoleum.com/product-catalog/consumer-brands/varathane/weathered-wood-accelerator

Here's a phenomenal tutorial- https://www.youtube.com/watch?v=v1Ubc44LFMU

Check out this project, I think it's the look you're going for-http://www.itallstartedwithpaint.com/vintage-look-crate-diy/

Okay. Every one of those professional ideas are great. I’ll just give you a redneck idea. I use redneck as a positive, practical, cheap descriptor. Drop your crate in a mud puddle for an hour. (Make a mud puddle in your yard or in a big pan. Just dirt and water.) Rinse the crate and set in the sun to dry. While it is drying, squirt a little motor oil, WD49, or kitchen grease/oil on the grate. Let that dry, too. When you are through waiting, wipe any oil not dry with an old cloth. Smear the oil around. For the gray stain, mix black and white liquid shoe polish (or paint) just a little darker than what you want. Mix 1/2 cup of shoe polish with 1/4 cup of water, even if it will not mix smoothly. Then paint the dry crate with this mix. Just dip your brush and paint. It will definitely be streaky, and a little of the mud and oil stain will show through, adding character and age to the crate. You can soften the look in some or all of the areas by rubbing the wet paint with a soft cloth. Let it dry and you are through. Voila’! Old gray crate. Best wishes ☺️