The problem with a dip is if you buy too early, it may still continue on a dip.

I completely agree with only using "spare" cash.

I previously tended to drip feed it into a downward market e.g. with a set amount to spend I would buy perhaps 30% initially, then 10% each day (or set time period) as I watched the market. If it keeps going down, then you are investing overall at a lower price than the start point. If it starts to go up, then increase your %'age so that you don't go over your original "buy in" price. You would have still bought some crypto at below your price then.

Do other people do this, or is it too much of a faff and you just buy in a single transaction when you think the market is at the bottom of a dip?