3betting and 4betting light as a bluff is not something you should do very often, unless you are confident that you can exploit other players tendencies.

Most low stakes players understand the importance of position and will raise in the CO/BTN with a wider range of hands, so you can can advantage of positionally aware players by 3betting light when they raise in late positions. You should only consider 3betting light when playing against fairly tight players who can fold to 3bets. It's pointless doing it against players who always call your 3bets, against these type of players you should only be 3betting for value.

4betting light can also be extremely profitable but should be used rarely. Players who have a high 3bet percentage are obviously 3betting light, not just their premium hands, so it can make sense to 4bet light against them.

In this particular hand I was dealt KTs. The player in the CO was a TAG and I knew they had a high fold to 3bet%, so when they raised which they would be doing with a wide range, it makes sense to 3bet light.

In the next hand, I was dealt KQo which is a standard raise on the BTN. The player in the BB decides to 3bet. I knew this player was capable of 3betting light, so they would be 3betting hands like AT/AJ which even though they have better equity then KQ, they will likely fold to a 4bet, and I also knew this player was always folding to 4bets, so in this situation it makes sense to 4bet light.

Generally you should consider 3betting and 4betting light with hands which you can not call with, and you know they player will likely fold to the reraise.