I usually tap the filter to remove dust and dirt but can they also be soaked in soapy water then air dried to clean better ?
They certainly can. Be sure to get them rinsed very well, remaining soap residue can really attract and hold the fines.
^^^^^^ what he said ! You can also use a bit of shop air to aid the fine removal ,and drying process . Go easy on the air . 15-30 psi ,and a little distance between the filter ,and nozzle .