1). H2O2 solutions > 30% w/w (like not correctly prepared, Piranha one), are metastable and self-explosives in any moment.
2). The most effective is chromosufuric acid but it is associated with cancerogenic and environmental (waste) issues.
3). You can use conc. H2SO4, (attention that H2SO4 is completely removed), water, acetone and dichloromethane or alternatively, by the inverse sequence. Optionally you can also use H2O2 solution < 30% w/w but this can lead to an exothermic Bayer-Villiger reaction if H2O2 is not completely removed before washing with acetone (note that glass fits dramatically increases the contact surface area or the reagents).