Mine is a mashup of these two patterns. I used more the shape of the FU mask, but had to modify it a lof to myself. DH and vet clinic staff are happy with size medium. Mine is based off size small - but I have a freakishly small head and wear children's size glasses, so... Definitely test it out for fit and be prepared to tweak your pattern.
I'm using 2 layers of shop towels - the blue paper towels that come in a box - for the filter. The material can block 93% - 95% of particles sized 0.3 microns. Translation - if your mask fits tightly to your face with no gaps, you might get as good of protection from this design as from an N95 medical mask. It's a helluva lot better than a cotton/flannel surgical mask.
I am using cotton jersey fabric (like a good quality t-shirt) for the inside and outside. The metal nosepiece is very important for fitting. I'm using "light duty soft wire tie"sold for staking plants.
I'm using strips of t-shirt material for ties. They're soft and stretchy and hold well. They're super fast to make. Cut 1" strip across the grain. Pull the ends to stretch it. It will curl up like a cinnamon stick - cut ends inwards. Looks decent and no-sew. 14" ties work with mine, but test it on your masks before you make a whole bunch!
Masks are less effective - possibly not effective at all - when damp. Change your mask every 2 hours. Workers who need them all day are recommended to have 6 per day.
Wash in regular laundry, with detergent is plenty. But if you feel like you need more, Lysol laundry sanitizer is on the EPA list of products that kill coronavirus. It has been more readily available in stores than other Lysol products.