Yes, you can use the past progressive/continuous or past simple tense to make a request or suggestion sound more polite, for example, you can say "I was wondering/I wondered if you could comment on my blog", instead of saying "You should try to comment on my blog".
In addition to 'I was wondering/I wondered', you could use 'I was hoping', 'I was thinking' or 'I thought' instead of 'I hope' or 'I think' to express politeness. That is to say, the past simple or progressive tense can have present o