Well you have a couple of options for colon cleansers.
OxyPowder is a good choice. It's a simple cleanse. Like you said you take some capsules before you go to bed.
Bowtrol is another colon cleansing that is simple. Similar to Oxypowder, you take some capsules at nite prior to bed. But it's slightly different then oxypowder, because Bowtrol is an Herbal Colon Cleanser. Oxypowder is an Oxygen Colon Cleanser.
Although, it must be noted that Bowtrol has some questionable herbs included in its formula. Cascara Sagrada & Senna are two ingredients that should not be taken excessively (7 days), and they are included in Bowtrol's formula. Keep in mind this is a 30 day colon cleansing program. I'm not saying that it would be unsafe to take this product, but it would be wise to double-check with your doctor prior to ingesting these two herbs.
Colpurin is another colon cleansing product that is pretty simple. There are two products you take, one you take the Internal Cleanse for 15 days and take the Total Body Purifier for a full 30 days. Colpurin also contains Cascara Sagrada.
Out of these three products, I would recommend OxyPowder. All of these products are around the same price range, none of them require you to mix fiber drinks or laxative teas, and are more convenient... which is what you are probably looking for. They are all effective in different ways. I would recommend OxyPowder because it is an effective process of colon cleansing.