If they are looking for short term profit then they will be disappointed and you are I know that for us to see reasonable profit in bitcoin investment we must invest for the long term and not short term. That's why it's necessary for people coming into bitcoin investment to have the right orientation/mentality. They have to know on time if are coming into bitcoin investment as a trader or hodler.
When it comes to knowing when to use the other two strategies like buying the dip or lump sum, well I will say that the person who is making his first buy in bitcoin can use lump sum buy and follow it up subsequently with DCA, especially if he wants to own a certain level bitcoin in his possession. While knowing when to use the buy the dip strategy is simply when you see the level of dip you have already predetermined or set for yourself before any dip occurs in the market. This will make you not to lose focus or confused on when to enter the market if eventually dip happens. You know nobody has the entire knowledge of the market and when certain variables will play out, so it's important to always get prepared before the eventuality of any market situation. When preparation meet performance, good result is always birthed.
Those who have spend time in Bitcoin have consent that it's ideal to invest into Bitcoin for long term. But that's not the case with new comers, most of them came with mind that Bitcoin is about getting rich overnight and when that desire is not fulfilled they get disappointed.
Regarding three techniques i.e. Lump Sum, Buy the dip and DCA, anyone with experience can adjust buy the dip and Lump Sum with DCA. If I am a new comer, I would prefer to go with small amount i.e. investing small amount every week or month. Once your confidence is developed you can go for Lump Sum with some increased capital. Both DCA and Lump Sum are good as long as you are confident about the technique you are adopting.
I think there are only two method that I know of which is lump sum buy and the DCA method. You mentioned buying the dip but this is also a lump sum buy that is done when price retraces after an upward movement. It is different from buying using the DCA method because it involves an instant order whereas the DCA is a continuous buying process that is done weekly or monthly as the case may be. Maybe there is further distinction between between buying the dips and other forms of buying that is done at once for which I consider less important so as to avoid memorizing too many things. Maybe for academic purposes, such distinction might even become necessary and there is nothing wrong about it.
A combination of both methods is possible but it requires someone with experience and discipline to do effectively. I will not recommend that for a newbie to avoid being emotional about the whole process, rather I will suggest focusing mainly on the DCA method that is easier to follow and produces outstanding results when followed dutifully. However, no matter what method is adopted, some level of effort is needed to be able to follow such method with a sense of responsibility.